42 



BOTANY. 



Win whole of IliR protop'asm of the mother-cell Is used. The former L& 



calls Free-OtU Fvrmation,a.nd. 

 the latter Formation of Cells- 

 by Divmoit of the Mather- 

 Cell, and includes also under 

 the last a part of what has 

 been described abr)ve under 

 the head of Fission. It is 

 doubtful, however, whether 

 such a division is of much 

 importance. 



(6) What has been called 

 the Rejuvenescence of a cell 

 may be mentioned here. The 

 phenomena connected with it 

 are as follows: The proto- 

 plasm of a Cell contracts, ex- 

 pels a portion of the water 

 contained in it, and escapes 

 through a slit in its wall ; the 

 naked mass becomes for a 

 time a free-swimming zoos- 

 pore, alter which it secretes a 

 wall of cellulose, and begins 

 to grow and form new cells 

 by fission. Cases of this kind 

 occur in (Edogonium, Stigeo- 

 clonium, and many other 

 aquatic Thallophytes. An 

 interesting fact, but proba- 

 bly of no great significance, 

 is that the axis of growth of 

 the new cell is perpendicular 

 to that of the old one. 



While there can be no doubt 

 that this process, as Sachs 



Pig. .32'-P«2TsrS«»«^/o.'^'ji. vertical section insists,* "must be regarded 

 of ihe whole plant; ft, hymenium- i.e.. the layer morphologically as the for- 

 iuwhi h the spore-forming sacK lie ,S. the tiesiie „„4. . n » ^i 



of the futiKus envrliiping the hymenium at its matiou ot ii new cell, there 

 edgeglnacuplikemanner;. at the baseof the can be little question that it 

 tissue S Are threads aiise. which grow between . , , , , ^ , . 

 the particles of earth. B, ii small portion of the is closely related to the forma- 



hymenium;/!A, 6ub-hym.niiil layer of denselyin- tion of zoospores described 

 terwoven filaments (hyphse) ; ffl to /, spore-form- ^ "v-owi,you 



ing sacs (am), with thin filaments (piraphyses) above (p. 40). The difier- 



belween them. AxW,Bx 550.-After Sachs, gnce is that in the formation 



of ordinary zoospores the mother-cell breaks up into more than 



* See "Text-Book," p. 9, and also "Lehrbuch," 4te Auf., where the 

 author sets apart this as an entirely different mode of cell-formation. 



