40 



A TEXTBOOK OF BOTANY [Ch. Ill, 5 



in an unl)rokcn protoplasmic succession to the very first 

 living organism of the earth. As to the source of the pro- 

 toplasm of that first being we know nothing, though we 

 have two h}'potheses, Ijoth of whicli maj' be groundless. 

 One relies upon an original case of spontaneous genera- 

 though perhaps never repeatetl. The other makes 

 protoplasm itself an evolu- 



tion, even 



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tion from earUer and simpler 

 sul:)stances, suited to the dif- 

 ferent earUer conditions of 

 the earth, and thus carries it 

 back to an origin contempo- 

 raneous and ecjui-causal with 

 the origin of non-living mat- 

 ter. The former is rather the 

 mechanistic, and the latter 

 the vitalistic view of the 

 sul.)ject. 



There remains one very 

 important characteristic of 

 protoplasm, and that is its 

 organization within the indi- 

 vidual plant or animal. In 

 most organisms the proto- 

 plasm is subdivided into the 

 microscopically small masses 

 constituting the cells. This 

 subdivision, however, is not complete, for suitaljle methods 

 always show that through the cell walls run protoplasmic 

 threads, which, though extremely fine, suffice to keep the 

 different cells in physiological continuity (Fig. 15) ; and such 

 threads seem to unite all of th(> living cells of a plant into 

 one prot(jpl:isniic system. 



Within each ctli t\\o protoplasm shows a definite organi- 

 zation, clearly e.xhiljited in typical form in our Figure 12, and 

 represented in principle in our generalized picture, Figure 16. 



Fig. 1.3. — .V typical example, in 

 Mistletoe, of the continuity of proto- 

 plasm by threads through the cell 

 walls. The walls have been made to 

 swell in order to render the threads 

 more clearly visible. (From Stras- 

 burger. Jest, Schcnck, and Karsten, 

 Text-bovk.) 



