40 



EOT ANY. 



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



come naked motile cells (/oospores) (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 



\\9 \ arise P'' IL ' IIL) ; between the 



\^ \ I.; nuclei may be seen a line indicat- 



\ mi. \ lelirei ing the separation of the proto- 

 plasmic mass into two halves. 

 Xext the nucleus in eacli 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 



Fi ? . SO.-Terminal cells of Achlya. used. One of the best known is 



c in the formation of ascospores. 



thc 



^ ; Here the mother-cells are usually 



of the daughter cells, from which ]) A ' the nucleus disappears, and 

 the content* have i-sciipert as motile , , . . ' , 



ceils (/.oos-pore^, , c, a young lat- the ])roto])lasm condenses in tlie 



era, branch, x 850.- After Sachs. 



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 



