DIFFERENTIATION OF ORGANS IN THALLOPHYTA 23 



desmid of only one cell-nucleus, whilst in the caulerpa there are many 

 nuclei. This clearly indicates a difference in degree of organization which 

 may be illustrated as follows: Let us suppose A to be a cell with 

 one nucleus and B to be a cell with many nuclei. Both may multiply 

 by swarm-spores. In B this may take place simply by each of the 

 cell-nuclei becoming surrounded with protoplasm, and the protoplasmic 

 body in this instance breaks up into isolated parts. In A, on the other 

 hand, a repeated series of divisions must take place before the same 

 result is reached. The plurinucleate cell is then in point of time ahead 

 of the uninucleate one in differentiation, and shows in the possession of 

 many nuclei a feature in its vegetative life that only appears in the 

 uninucleate cell at the time of propagation. The plurinucleate plant-body 

 does not correspond with the vegetative stage of the uninucleate cell, 

 but with that which this cell reaches just before propagation. These 

 reflexions lead us to Sachs' notion of energids. ' By an energid,' says 

 Sachs, ' I mean a single nucleus with the protoplasm it dominates.' These 

 energids may be enclosed singly or a number of them together in a 

 cell-chamber. It is not necessary that the mass of protoplasm 'dominated ' 

 by a cell-nucleus should be always the same l , but the behaviour of 

 the nuclei in the formation of the propagative organs of Siphonieae 

 indicates plainly the important influence the ' energids ' exercise in the 

 process ; and similar evidence is forthcoming from regeneration. Into 

 all processes of propagation which have been accurately investigated, 

 whether these be sexual or asexual, either single energids enter or, where 

 this is not the case, as happens with the swarm-spores in Vaucheria -, the 

 cilia indicate that we have to deal with a body which is not a simple 

 one but is composed of many energids. Our recently acquired knowledge 

 of the cell teaches us then that we must no longer distinguish between 



o o 



unicellular and pluricellular but between monergic and polyergic plants a . 

 Polyergic plants may be divided into cellular, which is the usual form, 

 and non-cellular groups, according as the energids are enclosed or are not 

 enclosed in chambers. Examples of polyergic non-cellular plants are the 

 Myxomycetes, if one reckons these as plants, and the Siphonieae, which 

 have only an external circumscribing membrane. Both these groups, it 

 will be noticed, are composed of organisms which are aquatic or dwell in 

 moist spots the Myxomycetes living concealed in these moist places until 



1 Rider and horse in a cavalry regiment form a ' unit' even although the horse be changed. 



2 Schmitz has proved that there are two cilia to each cell-nucleus, or as we now say to each 

 energid, and the whole pluriciliate swarm-spore is therefore composed of numerous biciliate ones. 

 The difference between monergic and polyergic cells shows itself specially in their behaviour in 

 ' regeneration.' In this process small portions of the contents of polyergic cells can grow out 

 to new cells according to the number of energids they contain ; in monergic cells such a breaking 

 up is not possible. 



3 Monergic and polyergic are shortened forms for monenergidic and polyenergidic. 



