40 



BOTANT. 



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 (I., 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 

 used. One of the best known is 



A. still closed, but with the ^roto- ^^ ^^^ formation of ascospores, 



Fig. 80.— Terminal cells of AchVya. 

 . still closed, but with the 

 pla^m in process of division ; 



^ISi^iTZiT&n^illtu] Here the mother-cells are usuaUy 

 at a the daughtHr-ceiis have juet large and elongated (Fig. 32, a, 



escaped : 0, the IhiTi cellulose wall-i o ^ \ o ^ ^ 



of the dauuhter-ceiia, from which J c) : the nucleus disappears, and 



the conteDts have escaped as motile ,t , ^ t • j.i 



cells (zoospores), « ,■ c, a young lat- tlie protoplasm conclenses m tne 



eral branch. X 550.— After Sachs. 7. „ , , ,t 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. 33) the protoplasm condenses 



