40 



BOTANY. 



after a little while they break their cellulose walls and be- 

 come naked motile cells (zoospores) (B, e). 



53. As the formation of the spores of Bryophytes and 

 Pteridophytes, and of the pollen- 

 cells in Phanerogams, is essen- 

 tially alike, we may take as an 

 example the formation of the 

 spores of a fern (Fig. 31). The 

 nucleus of the mother-cell first 

 disappears, and two new nuclei 

 arise (L, II. , III.) ; between the 

 nuclei may be seen a line indicat- 

 ing the separation of the proto- 

 plasmic mass into two halves. 

 Next the nucleus in each half is 

 absorbed and replaced by two, 

 between which a separation of the 

 protoplasm soon takes place (IV., 

 V.), thus dividing the cell into 

 four equal parts, which are at 

 first angular, but soon rounded 

 and enclosed in cell-walls (VI., 

 VII. , VIII. , IX.). 



54. In the foregoing cases the 

 whole of the protoplasm of the 

 mother-cell is used in the forma- 

 tion of the daughter-cells. There 

 are some cases, however, in which 

 only a part of the protoplasm is 

 Fig. 30. Terminal ceils of Achiya. used. One of the best known is 



A, Still Closed, but with the prOtO- j_j -Pnvmafi'rm r>f aonncmnvna 



plasm in process of division; 5, the m tllC lormation 01 asCOSpOieS. 



daughter-cells escaping through a TT orp f] 1p mnrlipr ppll<? nrp nsnnllv 

 rent in the wall of tiie mother-cell ; * "v 



at a the daughter-ceils hve just i ar <y e and elongated (Fig. 32, a, 



escaped ; 6, the thin cellulose wall-* v 



<>f the daughter-ceils, from winch J c) ; the nucleus disappears, and 



the contents have escaped as motile , ,, 



cells (zoospores), e ; c, a young iat- the protoplasm condenses in the 



eral branch. X 550. After fc>achs. , ,-\ ,-< n 



upper portion of the mother-cell ; 



in some cases (not in the species figured) nuclei appear, and 

 about these portions of the protoplasm gather to form the 

 ascospores ; in other cases (Fig. 32) the protoplasm condenses 



