HORTICULTURAL SOCIETY. 173 



PECULIAR ACTIONS OF SOME BLACKBERRY ROOTS. 



By Prof. Otto Lugger, Ph. D. 



There are many methods in which plants protect themnelves or 

 their offsprings against the severe cold of winter. Some species 

 of wild blackberries are very interesting in this respect, and as 

 some of the members of the Horticultural Society may be inter- 

 ested in such botanical investigations, the facts in the case are here 

 given and illustrated : 



Rubus bifrous, one of the species of blackberries, is shown on 

 the plate. In this case the ends of the branches are actually 

 pulled below the surface of the soil; this is shown in the illustra- 

 tion, by having removed the soil in such a way as to expose the 

 tips of the branches, and the roots proceeding therefrom. This 

 plant produces annually strong five-sided shoots, covered with 

 thorns, all pointing backwards. These shoots grow at first in a 

 perfectly straight and perpendicular direction, but towards autumn 

 they gradually bend more and more, until they form at last wide 

 arches, and thus the tips of all shoots come nearer and nearer to 

 the earth. Before such tips have reached the soil, however, we 

 can notice near the base of small, scale-like, and dwarfed leaves 

 little swellings upon the edges of the stems, which, when investiga- 

 ted a little more in detail, prove to be the starting points of roots. 

 As soon as a tip of a shoot has actually reached the soil, these root- 

 germs come in contact with it, and immediately commence to grow 

 and soon penetrate into the same. Here they elongate and grow 

 rapidly in size, numerous lateral branches are formed, and in a 

 very short time quite an extensive system of subterranean roots is 

 produced, as indicated in the illustration. But even the tips of 

 the shoots, from which the roots started, have been pulled beneath 

 the soil as well, and they now look quite fleshy and thickened. 

 These tips were pulled beneath the soil by the action of the roots, 

 and moreover remain embedded there. In the following spring, 

 and frequently already during a very favorable warm autumn of 

 the same year, these tips, nourished by their own new roots, com- 

 mence to grow, and soon form new plants which appear above the 

 soil. The old plant which produced such arched shoots, dies 

 sooner or later, and only the tips remain as new and independent 

 plants. 



But how can the roots pull such shoots below the soil ? And 

 there is not the slighest doubt that they perform this work. The 

 explanation is not a very difficult one: when ceasing to grow the 

 roots shorten, and in some cases this contraction amounts to nearly 

 one-third of the whole length. This shortening is produced by a 

 change in the turgidity in the cells during the absorption of 

 water. Whilst the cells of growing roots elongate by increased 

 turgescence, those of mature roots become shorter and broader 

 with an increase of turgity. It is indeed strange that in a mature 

 root the parenchyma cells during absorption of water, and an in- 

 creased turgescence, are made broader, and this at the expense of 



