FERTILIZATION IN PLANTS AND UNICELLULAR ORGANISMS 313 



two processes become closely apposed (Fig. 8i,a). The nucleus of 

 each cell moves into the bill-shaped process, is there transformed into 

 a nuclear spindle (B, Up) and divides, .so that on, daughter-nucleus 

 comes to lie in the apex point of the bill, the other at the has,. The 



eel -body also divides, though very unequally, and the 6nal out. ., 



ot the process is two cells in each, of which one is small and occupies 

 the apex of the bill, while the other is large and tills all the res! of 

 the cell-space. The former do not play any further part of importanc 

 but break up, the latter are the sex-cells, the cytoplasm of which now 

 coalesces through a gap in the cell-walls, while their nuclei become 



.■?.■< ?«f? £;k • f'Xr^#* ^ 



i — •>,£■•_*-'■ • - I., - 





Fig. 8r. Formation of polar bodies in a lichen, Basidiobohts ranarum. A, the tw. 

 conjugating cells with the bill-like processes in which the nuclei lie. B, the nuclei 

 dividing. Asp, the nuclear spindle. C, after the division into a polar body (rk and 

 a sex-nucleus (^ A and ?A;^. D, after the union of the nuclei to form a conjugation 

 nucleus (copk) ; the fertilized ovum is surrounded by envelopes and modified int<> 

 a lasting spore. After Fairchild. 



closely apposed and ultimately unite (C, J and ? 7c). From this union 

 arises the fertilized spore, the so-called ' zygote ' (J>). The two small 

 abortive cells so greatly resemble in their origin the polar cells of the 

 animal ovum that it is difficult to resist the supposition that they 

 bring about a reduction in the number of chromosomes. But tin- 

 number of the chromosomes has not yet been determined either in 

 them or in the sex-nuclei. 



We have come to know the processes of fertilization among 

 phanerogams chiefly through Strasburger, Guignard, and more 

 recently through the Japanese botanist Hirase. The agreement with 

 the animal process is surprisingly great, notwithstanding the notable 

 differences in the external conditions of fertilization. 



