43 



BOTANY. 



the whole of the protoplasm of the mother-cell is used. The former he 



calls Pree-Cell Formation,&ni. 

 the latter Formation of Cells 

 by Division, of the Mother- 

 Oell, and includes also under 

 the last a part of what has 

 been described above 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 9f 

 the new cell is perpendicular 

 to that of the old one. 



While there can be no doubt 

 that this process, as Sachs 



me.SS.-Pe,izaconvexula. ^, vertical section '^^^'^'s* ""^"f "^^ regarded 

 of the whole plant; A, hymenium- i.«. the layer morphologically as the for- 

 iiiwhi h the spore-forming sac lie, <S. the tissue „„*:„_, -f „ „„„ poll " tliere 

 of the fungus enveloping the hynienium at its niation ot a new cell, tuere 

 edge q in a cup like manner ; at the base of the can be little question that it 

 tissue S fine threads arise, which grow between . , , i ^ j i. *i r ™ 

 the particles of earth. B, «. small portion of the 33 closely related to the toima- 

 hymenium;«A, sub-hymenlttllnyerof denselyin- tion of zoospores described 

 terwoven filaments (hyphse) ; a to /, spore-form- , , ,„, mi j.jr 



ing sacs iasci), with tliin filaments (piraphyses) above (p. 40). The ditter- 

 betweeu them. ^ x 20, 5 x 650. -After Sachs, g^^g jg tij^t 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 aa an entirely different mode of cell-formation. 



