Chap, ii.] OF GROWTH IN THE VEGETAL KI>"GDOM. 277 



In germination, the cell emits from one point of its surface 

 a prolongation, a kind of protoplasmic rupture, which acquires 

 a nucleus, separates itself by partitionment from the rest of the 

 parent cell, and lives afterwards an independent life. It is by 

 this process that certain unicellular plants, for example the 

 Vaucherias, reproduce themselves. 



In the monocellular algae the spores and sexual cells, con- 

 taining antherozoids, analogous to the spermatic animalcules, 

 form themselves by the terminal partitionment of one of the 

 ramifications emitted by the cell. 



It is also in the algse, the conjugated diatomous algse, that the 

 phenomenon of conjugation is especially remarkable. Two 

 neighbouring cells each emit a prolongation ; these projections 

 meet ; their partitions are reabsorbed at the point of contact ; 

 the protoplasms of the two cells intermingle j soon the cells are 

 completely amalgamated. They then form only one cell, which 

 is a reproductive one, a spore or zygospore (spirogyra longatd). 



The multiplication of the cells, by endogenesis, is characterised 

 by the formation of a greater or lesser number of daughter cells, 

 which grow, burst the tunic, of the parent cell, and live in their 

 turn an independent life. This mode of reproduction exists in 

 some unicellxilar vegetals, for example, in the protococcacese.^ 



To sum up, all these diverse modes of proliferation do not 

 essentially difier from eath other. In every case the essence is 

 the same j it is a particle of living matter, individualised, which 

 assimilates beyond what is necessary for its own maintenance, 

 and becomes a true organic centre. Thus is produced an 

 exuberance of force and matter ; whence the tendency to the 

 formation of fresh centres. 



The growth of a vegetal, by the simple increase of volume of 

 the histological elements, may be considered as the first step, the 

 prelude to that development by cellular multiplications which we 

 have just described. Here also there is a predominance of the 

 movement of absorption, of assimilation. The nutritive liquids 

 1 Naegeli, Gfattimgen einzellvagen Algen, Zurich, 1847. 



