CONFER VOIDE.-E HE TER O GA ALE 



22! 



formed at the side, through which the colourless portion of the proto- 

 plasm protrudes in the form of a papilla which takes up the antherozoids. 

 In other cases the oogone splits in the same way as the zoosporanges, 

 throwing back a kind of lid ; through the lateral crevice exudes some 

 colourless mucilage in the form of a beak-like canal, through which 

 the antherozoids enter, and coalesce with the hyaline portion of the 

 oosphere. Immediately after impregnation the oosperm invests itself 

 with a cell-wall, and assumes a brown colour, still remaining within the 

 oogone, which separates from the other cells of the filament, and falls 

 to the ground, where the oosperm passes a period of rest before germi- 

 nation as a hypnosperm. 



Fig.. 202. — Biilbocli(ztc setigera Ag. B, unicellular aiitheridial plant. A, C, j-oung bicellular plants. 

 Z>, mature plant with oogone, o, and 'dwarf male,' dju (x 400'. (After Cooke.) 



In some species the mode of fertilisation is more complicated. 

 Peculiar zoospores known as androspores are produced non-sexually in 

 special cells of the parent-plant, similar to those which give birth to the 

 antherozoids, only that there is in their case no preliminary formation 

 of 'special mother-cells.' These androspores, which closely resemble the 

 antherozoids in form and size, fix themselves after swarming to a 

 definite spot on the female plant, on or near an oogone, producing very 

 small male plants, which are known as ' dwarf males ' or micrandres. 

 Each of these consists of two or three cells, the uppermost of which is 

 an antherid. This gives birth to one or more antherozoids, which escape 



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