38 RhodopTiycecB 



of the branches secondary branches grow downwards over the 

 main axis, forming a cortical ring of cell-filaments (sometimes 

 termed the pseudocortex). The apical cells of the lateral branches 

 are frequently produced out into long hairs or bristles. The pro- 

 carp is unicellular and is developed at the extremity of a small 

 branch which stands out directly from the main axis, and which is 

 termed by Sirodot the ' female axis.' The carpogonium possesses 

 a short, straight, exposed trichogyne 1 , and after fertilization it 

 develops the dense mass of gonimoblasts (frequently termed a 

 ' glomerulus ') which constitute the cystocarp. The cystocarps are 

 external, being developed amongst the dense whorls of branches, 

 and the terminal cell of each gonimoblast produces a carpospore. 

 On the development of the carpospores sporophytic shoots are 

 formed which very much resemble species of the genus Chan- 

 trim .via: they are to be regarded as a kind of 'protonema,' which, 

 under certain suitable conditions, develops into the sexual Batra- 

 cli osperrait w-plant. 



There are two more or less abundant species of the genus in the British 

 Islands, B. moniliforme Roth (Fig. 1 A) and B. vet gum (Roth) Ag. (Fig. 1 B), 

 each with a number of varieties. The latter is distinguished from the former 

 by the more or less uniform development of the lateral branches along both 

 the nodes and internodes of the inferior portions of the primary axis. A 

 third species, B. atrum (Dillw.) Harv., with very short lateral branches and 

 long internodes, is less widely distributed. Species of this genus commonly 

 afford a home for epiphytes of the nature of certain species of Calothrix, 

 Hapalosiphon, Ammatoidea, etc., and numerous Diatoms and Desmids are 

 frequently present in their enveloping mucus. 



Genus Chantransia Fries, 1825. The plants belonging to this 

 genus are much smaller than species of Batrachospermum and 

 occur both in fresh water and in the sea. The freshwater species 

 vary from about 3 to 7 mm. in length, and are usually found 

 attached to rocks and stones in rapid rivers, cataracts and water- 

 falls. The thallus consists of branched filaments of cells arising 

 from a basal stratum, the apices of the branches being frequently 

 much attenuated and almost piliferous. In colour the plants are 

 all shades of red, purple and blue. There is an entire absence of 

 the mucous coat which is so conspicuous a feature of Batracho- 

 spermum. It was thought for some time that all the species of 



1 Schmidle, 'Einiges iiber die Befruchtung, Keimung, und Haarinsertion von 

 Batrachospermum,' Bot. Zeitung, Heft 7, 1899. 



