208 STRUCTURAL BOTANY 



We see, then, that the production of the male cells 

 is a fairly simple process ; the female structures, 

 however, are much more complicated, and unlike any- 

 thing we have met with, so far, in any of our types. 

 The whole apparatus destined to form the fruit con- 

 stitutes a special branch borne laterally on an ordinary 

 filament of the thallus (see Fig. 90). The fertile 

 branch, which is called the procarpium, usually consists 

 in Callithamnion of five cells, of which three form a 

 central group, while the other two are situated laterally, 

 one on each side. The uppermost cell of the middle 

 row (see Fig. 90, a) is prolonged into a slender hair of 

 relatively great length ; this is the trichogyne (Fig. 

 90, t), or receptive organ; the lower part of the same 

 cell is somewhat enlarged, and bears the name of 

 carpogonium, because the development of the fruit starts 

 from it. The two cells next the carpogonium remain 

 small, and together constitute the trichoplwre ; the two 

 lateral cells are known as the auxiliary cells, because, 

 as we shall see, they contribute in a very important 

 way to the formation of the fruit. The description of 

 Fig. 90 should be carefully studied, to render the com- 

 plicated arrangement intelligible. The carpogonium has 

 a single nucleus ; the trichogyne which forms the upward 

 prolongation of the same cell has, in this case, no nucleus 

 of its own, but contains a strand of protoplasm continu- 

 ous . with that of the carpogonium below ; the outer 

 layers of its membrane are gelatinous. 



In this condition the procarpium is ready for 

 fertilisation. The long trichogyne is specially adapted 

 for receiving the spermatia. The young fruit is 

 generally placed in a sheltered part of the thallus 

 (as, for example, in this case, among the densely 



