40 



BOTANr. 



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- 

 l)lasmic mass into two halves. 

 sText the nucleus in each half is 

 xbsorbed 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 



wholef of the protoplasm of the 



mother-cell is used in the formar 



tion of the daughter-cells. There 



are some cases, however, in which 



only a part of the protoplasm is 



Kg.ao.-Tenninaiceiisofxrfjftyffi. used. One of the best known is 



pik^mint"-B',,faM^^^^^^ the formation of ascospores. 



fenlhl wSnTrfuXtii • Here the mother-cells are usually 



at a the daugiit r-ceiis have juet large and elongated (Fig. . 33, a, 



escapKi : b, the thin cellulose walN ° ° .^° '' 



of the dauahter-ceiiB. from which J c) ; the nuclcus disappears, and 



the contents have escaped as motile ,, , ■ -, , • ,-, 



cells (zoospores), « ; c, a young iai> the protoplasm condenses m the 



eral branch. X 560.— After Sachs. ,• » /t .i n 



upper portion oi 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 



