DIV. I 



THALLOPHYTA 



425 



Algae can be recognised, according to N. SVBDELIUS, when their development is 

 taken into consideration and they are compared in the light of the first nuclear 

 division in the rudiment. The young carpogonium contains two nuclei, of which 

 that belonging to the trichogyne later degenerates. (The uninncleate carpogonium 

 of Batrachospermum is apparently an exception.) The trichogyne corresponds 

 morphologically to the spermatangium, and its ventral portion to the basal or 

 mother cell on which one or more spermatangia are situated. The trichogyne and 

 egg-cell are only separated by a cell wall after fertilisation ( 496 ). 



The formation of the antheridia ( 49a ) as well as of the frequently very com- 

 plicated cystocarps follows a variety of types in the Florideae. In all cases, 

 however, according to OLTMANNS, the carpospores are to be regarded as derived in 

 their development from the fertilised egg-cell. 



Dudresnaya coccinea, which is found on the warmer coasts of Europe, has a 



FIG. 367. Batrachospermum moniliforme. A, Young carpogonium terminating a branch. B 

 Ripe carpogonium; t, trichogyne. C, Stage after fertilisation by the spennatium (s), the egg, 

 cell (o) containing the two sexual nuclei. D, Gonimoblasts (g) and investing filaments (h). E, 

 Some of the mature gonimoblasts with the carpospores (fc) ; these have emerged from ki and ^2- 

 (A-D x 960, .Ex 720. After H. KYLIN.) 



branched, cylindrical thallus and will serve as an example of the more complicated 

 mode of origin of the spore -bearing generation (Fig. 368). The carpogonial 

 branches consist of about seven cells, the terminal one bearing a very long 

 trichogyne. After fertilisation the carpogonial cell grows out into a filament, 

 which elongates and becomes branched. This filament fuses with a number of 

 special cells, characterised by their abundant contents, the AUXILIARY CELLS. The 

 first of these lie in the carpogonial branch itself, the others in adjoining lateral 

 branches. All the nuclei of the sporogenous filament are derived by division from 

 that of the fertilised egg-cell. The successive fusions with auxiliary cells do not 

 involve nuclear fusions, but simply serve to nourish the sporogenous filament. A 

 second and third sporogenous filament may arise from the carpogonial cell. Two out- 

 growths now arise from each of the swollen cells of the sporogenous filament 

 which fused with auxiliary cells. By further division of these outgrowths the spherical 

 masses of carpospores, which subsequently become free, are derived. 



In all Red Algae, as has been seen above, two generations can be distinguished, 

 the GAMETOPHYTE, which produces the egg -cells and the spermatia, and the 

 SPOROPHYTE, which proceeds from the fertilised egg and produces the; carpospores 



