ALGAE. RHODOPHYCEAE. 



77 



The simplest mode of formation of procarp and carpospores is exemplified in the 

 BANGIACEAE, which contain two genera, Bangia and Porphyra 1 , the former consisting 

 of cell-filaments, the latter of simple cell-surfaces. The spermatia are formed by the 

 division of a cell of the thallus into a number of small daughter-cells ; the division is 

 accompanied \\ ith loss of colour, and the daughter-cells are set free by the dissolution 

 of the wall of the mother-cell. The procarp is distinguished from the vegetative cells 

 of the thallus only by a small protuberance which represents the rudimentary tricho- 

 gyne. After a spermatium has coalesced with this protuberance, the carpogenous cell, 

 in this case almost the only representative of the procarp, divides into eight spores, 

 and these are ejected from the mother-cell as round, naked protoplasmic bodies, 

 which for a time display amoeboid motion, and then become invested with a cell-wall 

 and germinate. It is evident that this case differs only in subordinate points from the 

 mode of sexual reproduction in Oedogonium, for example, or Sphaeroplea. That the 

 male element in Bangia is not a spermatozoid, but a non-motile spermatium, is con- 

 nected with its mode of life, and, as regards the trichogyne, we find an arrangement for 



JL 



I 



FIG. 49. Nemalion multifidum. I a branch with carpogon c and spermatia ip. II, III commencement of the 

 formation of the fructification. IV, /-'development of the spore-cluster, t everywhere denotes the trichogyne, c the 

 carpogone and fructification. After Thuret and Bornet. 



conducting the male cell in Oedogonium, Coleochaete, and others ; that there is no open 

 passage in Bangia is connected with the want of active movement in the spermatium, 

 which would render special contrivances necessary if the spermatium was to find its 

 way into such a passage. Then the fertilised carpogenous cell of Bangia behaves just 

 like an oospore of Oedogonium &c., only that the latter when it has passed through its 

 resting stage breaks up into a number of daughter swarm-cells, each of which produces 

 a new plant. Besides the carpospores the Bangiaceae possess asexual gonidia formed 

 by the division of a mother-cell into eight ; the fresh- water species 2 have only these 

 asexually formed spores. 



The NEMALIEAE also have a unicellular procarp, but they are distinguished from 

 the Bangiaceae by the development of the trichogyne and by the production of spores 



1 Janczewski, Etudes anatomiques sur les Porphyra (Ann. d. sc. nat. ser. V. T. XVII). 

 Berthold, Zur Kenntn. der Bangiaceen (Mittheilungen der zool. Station zu Neapel, Bd. II). 



2 These grow in springs, on mill-wheels, and on the walls of canals, &c. 



