52 MANUAL OF BOTANY 



A complex procarpium is formed, consisting of carpogonial 

 branches and certain cells which ultimately give rise to the 

 auxiliary cells. The latter are not developed till after the fer- 

 tilisation of the carpogonium. AVhen they are complete, conju- 

 gation takes place between an ooblastema filament from the 

 carpogonium and either the auxiliary cell or a process growing 

 out from it. In some cases the carpogonial and auxiliary cells 

 coalesce without the intervention of either outgrowth. After the 

 process of conjugation is accomplished, gonimoblasts grow out 

 from the resulting cell and form a much-branched collection of 

 filaments which generally protrude from the thallus. Each 

 gives rise to a number of carposporangia. The thallus tissue 

 sends out filaments which coalesce round the cystocarp, forming 

 a protecting wall or case {fig- 800, LejoUsia). In some cases 

 where the cystocarp is formed upon a slender leaf-like branch 

 of the thallus the filaments proceed from near the cell which 

 bears the carpogonial branch and curling over the latter cover it 

 in. The wall generally begins to be formed as soon as the 

 carpogonium is fertilised. In some cases no protective coating 

 is formed. 



The most complicated type is met within the CRYPTONEMiACEiE. 

 The fertilised carpogonium sends out a very long ooblastema 

 filament which branches copiously, and consists of several cells. 

 There are many auxiliary cells formed upon separate branches, 

 and one ooblastema filament communicates Avith several of them, 

 fertilising several in succession. From each of these gonimoblasts 

 proceed ; and these branch repeatedly, the cells of the branches 

 formmg carposporangia, each contaming a single carpospore. 

 The gonimoblasts ramify in the substance of the thallus, so 

 that the fructification is internal, and surromided by thallus 

 tissue. 



The Corallines form a very special family of this group. 

 Their thallus, which is of very various form, is encrusted or 

 impregnated with carbonate of lime, the coating covering every 

 part except the reproductive organs. They bear curious cysto- 

 carps, which are really compound, and resemble the conceptacles 

 of Fucus. In the hollow of the conceptacle, which opens 

 apically, several carpogonia occur, each with its trichogyne. 

 Other filaments only produce auxiliary cells. After a carpo- 

 gonium has been fertilised it fuses with many of the auxiliary 

 cells by means of a single ooblastema filament, and a single 

 large cell is formed. The gonimoblasts, each of which bears 

 a chain of carposporangia, arise in some numbers from the 



