THE VEGETABLE CELL. 107 



the natural course of vegetation, varies extremely in diflFerent 

 plants, while at the same time we are unable to find a reason for 

 this vaiiation in the organization of the particular species of 

 plants ; in many species, for instance in the rooting of Caetese, 

 Willows, &c., this development takes place so readily, that it can 

 be counted on with the greatest certainty, while in others the 

 development of the wanting organs, for example, of roots and still 

 more of leaf-buds in Pmus, never or but very rarely occurs. In 

 general the formation of the said organs takes place the more 

 readily the richer the detached part is in parenchymatous cellular 

 tissue, and the more assimilated nutiiment there exists deposited 

 in it, at the expense of which it may be sustained until the organ 

 necessary to make it a complete plant is formed ; but tliis rule is 

 only valid for the extreme cases, and, mostly, we cannot say 

 what is the reason, they are readily or not all inclined to such 

 production. 



In very many plants, the formation of buds, which grow up 

 into distinct plants, is a regular operation, independent of external 

 causes. These frequently separate spontaneously from the parent 

 in a rather rudimentary condition, ^d grow into independent 

 plants subsequently ; in other cases, ^ch separation occurs after 

 the parent plant is dead and decayed, through particular ramifica- 

 tions of it remaining alive. 



In the plants having a thallus, we meet with the formation of 

 shoots which have not the form of the ordinary branches, but in 

 which the formation of the parent plant is repeated. Thus, in 

 the Algse, new plants are not unfrequently produced, both from 

 the ftond and from the disk-like base of this, or out of stolo- 

 niferous prolongations of it In the Liverworts and Mosses it is 

 a very general condition for single branches, the so-called innova- 

 tions, to lepeat the form of the main stem, and when this decays, 

 to appear as the stems of new plants. In the higher plants, 

 ramifications very frequently occur, deviating in form from the 

 ordinary leafy branches, and destined to serve for the multiplica- 

 tion of the plant. They present themselves either in abbreviated 

 and thickened forms (as bulbs and tubers), in which case they do 

 not generally produce roots of their own untiL detached from the 

 parent, or, on the contrary, they exhibit a predominant longitudi- 

 nal growth (as runners or stolons above or below the surface of 

 the ground), in which case, roots are developed, and they sustain 

 themselves independently before their separation from the parent. 

 The branches destined to the multiplication sometimes spring 

 from the normal place, from the axis of a leaf (e. g., the bulbels 

 of Lilium tigrinum) ; sometimes they originate from abnormal 

 metamorphoses of flower-buds (the bulbels of the inflorescence of 

 many species of Allmm, the tubers of Polygonum viviparwn) ; 

 sometimes they break out, as the so-called adventitious buds, 

 from spots which do not normally bear buds. The latter occurs 



