BATKACHOSPEEME^E,; COLEOCELETACEJE ; CHAEACE.E 575 



A very singular relationship, called by some writers an ' alter- 

 nation of generations,' exists between Batrachospermum and Chan- 

 transia, a genus of fresh-water alga? previously placed in a totally 

 different section. This relationship was first described by Sirodot, 1 

 and his observations have since been confirmed by others. The 

 germinating spores of Batrachospermum put out, under certain 

 conditions, a. kind of filament, known as n proton erne, which develops 

 into a Chantransia, a non-sexual form of Batrachospermum, which 

 can reproduce itself from generation to generation by simple 

 budding, or by means of non-sexual spores, without producing 

 sexual organs. Ohantransia is especially found in water where very 

 little light reaches it. When more exposed to light it undergoes 

 metamorphosis, and then a branch springs up from the protoneme 

 which is in every respect a Batrachospermum, bearing true sexual 

 organs, as above described. 

 This may then go on repro- 

 ducing itself, or revert to the 

 O.hanfransia form. 



The Coleochaetaceae are a 

 small order of fresh - water 

 Algfe, chiefly represented by 

 the genus C'oleochcete, which 

 forms minute discs or cushions 

 attached to submerged plants, 

 from -j 1 -^ to ^ inch in diameter, 

 consisting, in the simplest 

 forms, of a single layer of cells, 

 often arranged in rays proceed- 

 ing from a common centre. 

 Reproduction takes place non- 

 sexiiallv, bv means of zoospores, 

 or sexually, by the fertilisation 

 of an oogone by motile anthero- 

 zoids, through the agency of a 

 peculiar tube known as a trichogyne, a forecast of the more com- 

 plicated process which we shall presently meet with in the Floridese 

 or Rhodospermese, the highest class of Alga?. 



Among the highest of the Alga? in regard to the comph-xitv of 

 their generative apparatus, which contrasts strongly with the general 

 simplicity of their structure, is the family of Characeae,- some 

 members of which have received a large amount of attention from 

 microscopists on account of the interesting phenomena they exhibit. 

 These plants are for the most part inhabitants of fresh waters, 

 and are found rather in. such as are still than in those which 

 are in motion : a few species, however, may be met with in 

 ditches whose \\atcr> are rendered salt by communication with the 

 sea. They may be easily grown for the purposes of observation in 



1 Sirodot, Lcs BatracJiosprrniees, fo. 1884. 



2 [Many of the best authorities regard the Characeer, in consequence of their 

 mode of reproduction, as a group of primary character, of equal rank with the Algee, 

 and superior to them in organisation. ED.] 



FK;. 433. 

 Batrachospermum. nionili forme. 



