Leaves are simple, little variable as a rule and only on sprouts irregularly lobed, alternate, on the dorsal side dark green, rough, pubescens, on the ventral side lighter, paper-leathery relatively hard, petiole 10 to 15mm long. Leaf blade is broad - ovate, 100 to 150mm long, 100 to 120mm wide with cordate base and shortly acuminate apex. The leaf margin is crenulate dentate (crenate dentatus) (Kavina, 1951). Flushing of leaves begins as a rule in the second half of May, so compared with other woody plants much later. This fact was noticed already by ancient Romans when Plinius named this mulberry as "sapientissima arborum" (the wisest of all trees).

Nearly simultaneously with leaves development also unisexual, monoecious flowers composed to headform spikes begin to break. Male flowers bear 4 stamens and are diffused among female ones which consist of upper ovarium with two styles bearing shortly pubescens stigmata. After pollination (by wind or insects) and fertilization, petals of female flowers become fleshy, enclose wholly ovate key fruit and all inflorescence turns to the known composed fruit - mulberry (sorosus) - 35 mm x 20 mm, significantly cylindrical with short petioles.

On unsufficiently nourished branches fruits are smaller and more spherical. Light - green colour of young fruit transforms in course of development to light-pink, later to dark red and in full ripeness to dark purple. Fruits ripe gradually from mid - July to September. Red fruits are very acidic but during ripening acid concentration decreases and in full ripeness the fruit is sweet and only slightly acidic with characteristic flavour and high content of bloody coloured juice. Fruits are easily to separate from shoots only in the full ripen state.

The wood of black mulberry is circularly porate with the yellow-brown core and yellowish young wood. Annual rings are clearly visible with thicker layer of late wood and thinner layer of spring wood. Pith rays are distinguishable with the naked eye. Pith is relatively thick. Vessels are circular on transversal section. In primary bark and in floem latex-vessels take place. The wood is relatively hard, medium heavy, very bad splitable, tough, on longitude sections shiny and very durable. Evidence of this are died and untreated parts of trees which neither over decades succumb to rot and their wood remains still hard and firm. On died wood no wood destroying fungi, no pests either no holes after woodpecker have been found. The wood of black mulberry is heavier and more durable than wood of white mulberry. Microscopical structure of both species is the same. On the first look the mulberry wood is very similar to acacia wood. The grey bark of young trunks becomes thick relatively fast (up to 20 mm) and forms thick, longitudinally dissected suberized bark. The bark of roots is orange - yellow. Roots with their length considerably exceed circumference of the crown (Balabán, 1955).

The origin of black mulberry is unknown as Iran being sometimes reported has not been proved. Zelený and Grünerova (1982) have stated that it has been largely grown in West Asia (although very often West Asia has been taken for its native hand) in northern part of Arabian peninsula (Lebanon, Jordan, Syria) in Afghanistan, Iran, Middle Asia and in Caucasus. Domin (1948) has reported that black mulberry grows wildly evidently in south part of Trans-Caucasus e.q. Carabakh, Talysh but in the remaining part of Caucasus region is only rare (?). Kolesnikov (1960) has reported about it only like about cultivated woody plant namely on Caucasus, the Crimea, Middle Asia, rarely in the Ukraine and in some botanical gardens (Odessa, Kiev, Lvov other). However in Odessa during cold winters has been killed by frosts. Some data on black mulberry in China have been probably false as it is not known that this species has been grown in China. The black Chinese mulberries, taken for M. nigra, are probably red - fruit forms of white mulberry.

As early as in antiquity black mulberry had moved from its mother land to Greece and from here to all Mediterranean area. In antique it was well known, as Teophrastos, Plinius, Horácius, Vergitius and Columella had reported on it. Hence, name Morus relates always only lo black mulberry, as white mulberry started to be cultivated in South Europe in about the 12th century and in Middle Europe only since middle of the 16-th century. Red mulberry (Morus rubra) native to Northern America has been reportedly grown in Europe since 1629 (Klika, 1947). Probably from Italy black mulberry got to southern and northern part of Germany. Its main disseminators were monks, who reported about it as a medicinal plant. As early as in the 5th century the mulberry vine "moretum" was known on territory of Germany. In 1912 Geisenheimer described a tree of black mulberry from the west part of Germany, which "lies" and which, people say about it, is at age of 1000. Although this age was exaggerated it surely had been yet in that time a very old tree. The same author reported that black mulberry occurred in Germany-Rhone, in Harz mountains, in littoral regions on Helgoland island.

By Kovalovský (1960) it grows yet under temperate climate of southern Sweden and isolately in Switzerland. Its occurrence in South-European countries (Greece, Italy, Bulgaria, Yugoslavia) is limited; in Hungary and Germany is rather scarce. In Poland is unknown, Pilát (1953) has reported this species was introduced in our country from West Asia in 1548.

Occurrence in former Czechoslovakia in west Slovakia it commences with isolated trees in surroundings of Nové Mesto nad Váhom and continues over large interspaces, with warm exposures of Small Carpathian Mountains where within the land register of village Dolné Orešany, on grounds of former vineyard, by Kovalovský about 50 very old trees still in 1960 have grown. This region continues through Častá, Modra up to Bratislava and Skalica. Middle Slovakia region commences with isolated trees in surroundings of Modrý Kameň and continues through Krupina, Bátovce, Jabloňovce, Bohunice, Pukanec, Devičany, Nová Dedina, Čajkov, Rybník, Levice, Hronský Beňadik, Zlaté Moravce, Vráble, hill - side of Zobor by Nitra and ends with several trees near Hlohovec. Isolately it occurrences also in neighbourhood of Štúrovo and probably in vine - regions of east Slovakia (Zelený and Grünerová, 1982). However reliable proofs on its occurrence in east Slovakia are missing.

In Moravia, black mulberry grows only in the warmest regions namely in villages Bohutice, Miroslav, Vnorovy, Orechov, Žeravice, Kounice, Styrovín, Újezd, Hostějov, Dobromilice, Sokolnice a Židlochovice (Zelený and Grünerová, 1982).

In Czech country it grows in the surroundings of Prague - Brezhany u Zbraslavi, in Czech Central Montains at Raná u Loun (here it grew a tree 7 meters high with circumference 2.9m which died due to frost damage in 70s), Miřejovice, Litoměrice, Velké Žernoseky, along Ohře river valley in Červený Hrádek by Chomutov, Chomutov (Zelený and Grünerová, 1982).

The richest locality at all on the territory of former Czechoslovakia is the landregister of town Pukanec, where on the south slopes of Štiavnica Montains, by counting in 1986, 460 yielding trees grow. Trees growing in own town estimated for 40 to 50 individuals were not involved into the total number. Majority of trees is at the age of 100 to 350, although some individuals for their mighty growth would demand a higher estimate.

Majority of black mulberry trees grown within Pukanec territory take place in cultivated vineyards, eventually in former vineyards and only minority in home gardens and yards within territory of town. Locality is situated at an elevation of 330 to 480m, on slopes exposed to south, south - west and south - east. Black mulberry has similar climate demands as apricot.

Winter frosts damage it only in case, when temperature drops to -25°C and more. During severe winter of 1928 -1929 in range of one month reached air temperature in Pukanec -30°C. However only young trees in overfertilizated soils of gardens succumbed to frost killing while on trees grown in poor soils of vineyards only young shoots frosted. During winter 1955 - 1956 there was in Pukanec recorded temperature -26 C and on mulberries only flower - buds frosted, so in that year there was no fruit yield. A fall of temperatures to -20°C up to -22°C during January and February of 1985 did not cause any injury of mulberries as in that year a good fruit yield was recorded.

Pukanec area of black mulberry can be ranked to warm climatic region, warm, mild humid district, with mild winter. Average year temperature is +8 °C to +9 °C, average temperature in vegetation period is +16°C. Temperatures of the coldest months (January, February) only rarely overtop -20°C, while summer temperatures very often reaches 34°C to 35°C. Average sum of year precipitations is 681mm, in vegetation period 300 - 350mm. Snow cover lasts in average for 75 days and its mean thickness reaches the highest value in February, namely 80-120mm. In December and March there are relatively few days with snow cover (Kolektív, 1958). Flowers injury with late frosts were not observed as well as frosting of current shoots due to early frosts, which come in this region very late and current shoots lignificate in time. Within territory of Pukanec black mulberry grows on poor soils which are often stony, rather permeable and dry, shallow to average depth. Andezites and especially propyliritate andezites (SW - part of vineyards), which form geological basis of Pukanec region, have been, from the chemical point of view, ranked to the group of siliceous minerals without calcium carbonate. According to nutrient analysis, andezite minerals of this region and soils derived of them have moderately rich mineral content.

Probably the oldest documents on existence of black mulberry on our territory come from the last century (Strelka, 1984); in 1839 Molnár in both "Fatenyesztés", in 1893 in Journal "Gyúmelcsekertészet" and then in 1910 Szántó Peter in publication "A begyés gyümöIcsök tenyntése", in 1911 in Journal "Kiss kertész", in 1922 Szecsényi -Wolkenstein in book "Törpe gyíimôlesfák ültetése" all have named black mulberry with adjective "sour" eventually sour "Spanish" or "Turkish". J. L. Holuby "tutor" of Slovak botanists, correctly determined Morus nigra from Pezinok as early as in 1910 (Zelený, !985). Dr. Zelený has reported that probably the first one who had directed attention towards this species was Jablonský in 1936. This priority is however by Strelka (1984) problematic. In 1947 Czech botanist Karol Domin obtained a fruiting twig of black mulberry from Častá near Trnava, where this species was called "tree raspberry" Domin (1948) after scrutiny of obtained material and on the basis of obtained information assessed that this species by its characters ranks to the group of black mulberry. However at the same time he found out that it showed some characters indicating red mulberry (Morus rubra) but also other characters which differ it from both mentioned species. So he got convinced, it was, to that time a not described type of mulberry which deserved appreciation as a new cultivated species. Putatively by its characters it can be assessed that it generated from the crossing M. nigra x M. rubra and that it is a hybridous species with certain special characteristics. He named it: Trnavas mulberry - Morus trnaviensis DOM. Later, thorough analysis proved that described species was a typical representative of M. nigra L. which Domin had not recognized. (Zelený and Grünerová, 1982).

The first who had directed attention to Domins mistake was Kovalovský (1960) who on the basis of findings from German, Polish, Soviet and English dendrological literature as well as from key descriptions of Hungarian literature has stated, that there reported systematic descriptions of black mulberry (Morus nigra) are in accord with Domins description of Trnavas mulberry (Morus trnaviensis). He claims that Trnavas mulberry is no new Slovak species of mulberry but it is true Morus nigra named by Linne. So name Morus Trnaviensis remains only synonym for black mulberry distributed not only to Slovakia, Czech and Moravia but nearly all over the temperate Europe. Others who pointed at Domins mistake, were Pilát, Hrubý, Kamínek M., Kamínek L. (Zelený and Grünerová, 1982). However Pilát and Hrubý omitting preceding verifying of problem formerly accepted M. trnaviensis and then immediately unscientifically rejected (Strelka, 1984). Simultaneously with Domin, distinctness of Trnavas mulberry was conducted by Prof. Dr. Novák who had come to the same opinion like Domin did. Zelený (1985) has however reported, that description of Novák brought no taxonomic solution. Hybrid origin of M. Trnaviensis from M. nigra x M. rubra L. is not likely, as M. rubra with its character complex gets much closer to M. alba than to. M. nigra regardless of great difference in chromosome number (M.rubra 2n=28, M. nigra 2n=308). Benčať (1968) has reported it cannot be omitted impact of the changed ecological conditions compared with original area and selection although negative done by fruit growers, what both could led to producing of particular new properties not fully consistent with the type nevertheless not such ones to be taken for species characteristics. As the question is not yet definitively and satisfactory answered in terms of current nomenclature of plants it is proposed to accept its new name Morus nigra cv. Trnaviensis. Zelený (1985) has assumed that comparison of Middle European populations of M. nigra with Near East population is still not fully answered question as from the latter region herbarium material is still insufficient. Kamínek's brothers who in 50s thoroughly studied so called Trnavas mulberry, had opportunity to compare growing trees of M. nigra in some Arabian countries with those from our county and they found no differences (Kamínek and Kamínek, 1968). Hence so far it is no use to consider Trnavas mulberry for a cultivar of black mulberry.

As it can be seen views on origin of this mulberry differ and one of them even admits it is a triploid form of Morus nigra (Šimánek et al. 1977). Data on chromosome number in taxa of genus Morus affirm that M. nigra is polyploid (Table 1). Black mulberry is a species with low diversity, cultivars are not known.

Fruits of black mulberry are easy digcstible, refrishing. eatable as natural or processed for stewed fruit, juice (sterilized or not sterilized, thickened by sugar) less frequent for vine (vinum moratum). As early as Old Romans imputed good digestive and antitoxic effects to the fruits. At present fruits are valued as moderate laxative and expektorative. To the decoction from the dried leaves adstringent (contractory) effect and control effect on blood sugar level has been imputed and therefore has been recommended by diabetes and diseases of pancreas. Chemical composition of fruits is as follows (in %) (Němec et. al., 1958): water - 78, dry matter - 22, comprising sugars - 18, organic acids - 0,85, mineral subsiances - 0.32 nitrogenous compounds - 1.4, oil in seeds - 30.6 (computed from seed weight). Vitamine content analyzed in 1 / mg.100g is as follows: vitamin C - 3.8 (by Shall up to 20), B1 - 24, B5- 5,3, B6 - 1,5, Ieaf acid - 450, Beta carotene 0.025; vitamin E (tocoferol) in seeds 0,279%.

Of mineral substances it is especially important potassium content which is in black mulberry up to 300 mg per 100 g. Its shortage first of all is evident in elderly people and has been manifested with weakness feelings, sometime with hearth arythmic and often with higher blood pressure (Kresánek, 1977).

The most frequent and most proved way of propagation of black mulberry used in Pukanec is layering eventually heaping. These ways suit to trees which produce stool shoots near to ground. All trees Pukanec black mulberry are own-rooted, what means they originate either by layering or heaping (Zamboj et. al., 1975). Another way o propagation is rooting of young suckers growing from stump of cut tree. The suckers being heaped on their basal part with soil easy root and after good rooting can be separated from the mother stump. Various ways of propagation, but especially propagation by graffing and budding have bean in details reported by Kovalovský (1960).

Black mulberry is an perspective fruit crop for garden - owners and fruit growers in climaticly suitable regions of Slovakia. As there is still more interest of this fruit crop among fruit - growers and admirers of this excelent fruit, it would deserve much more attention than until now as regard its cultivation, distribution but mainly conservation of present old plantings at its historical localities.

References

Pilát, A.: Listnaté stromy a keře našich záhrad a parku. Štát. zemédél. nakladatelství Praha, 1953
Strelka, F.: Niekoľko poznámok k Článku Dr. Zeleného, "Dreviny z Čclede" moriišovjtých pestované v Československu". Dendrologická sdélenŕ 30/1984
Šimánek, J. a kol.: Menej známe o'vocniny. Príroda Bratislava, 1977
Zamboj, J. a kol.: Pukanec. Pamätnica k 30- výročiu oslobodenia. Osveta,n.p. Martin, 1975
Zelený, V.; Grúnerová, M.: Dreviny z čeledě morušovitých pestované v Československu. Fólia dendrologica 8/1982
Zelený, V.: Odpoveď Ing.F.Strelkovi na jeho poznámky k článku V.Zeleného a M.Griünerové: Dreviny z čeledč morušovitých pestované v Československu. Dendrologická sdelenf, 1985

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