Notes on Floridex. By George Massee. 565 



ment ; but towards the base of the genus we have C. rothii, in 

 which antheridia and cystocarps are unknown, but characteristic 

 tetragonidia ( = tetraspores) are present ; yet lower down we meet 

 with plants agreeing exactly in thallus structure with C. rothii, 

 but without cystocarps, and instead of producing tetragonidia, we 

 find undivided gonidia produced in cells terminating lateral branches, 

 and occupying exactly the same position as the tetragonidia in 

 C. rothii. The species with undivided gonidia and no sexual 

 organs, including the old Callithamnion virgatulum of Harvey, 

 and others, now constitute the genus Trentepohlia. The asexual 

 or Chantransia stage of Batrachospermum can reproduce itself for 

 several generations by sporules, and continues to do so when 

 growing in dark or shaded situations, while the sexual or Batra- 

 ehosjoermum stage is mostly produced when growing in the light. 

 On this account it is difficult to demonstrate the genetic connection 

 between the two stages, which, however, has been done by Sirodot * 

 in several species, and he considers it as a true example of alterna- 

 tion of generations. This of course depends on the author's defini- 

 tion of that term ; it is certainly not in any sense an example of 

 alternation of generations as defined by Sachs,t where during the 

 entire course of development, the plant starts twice from a single 

 cell ; the first or sexual stage from the germination of a spore, the 

 second asexual stage from the oospore. In Batrachospermum, 

 the sexual stage is developed last, and not from a single cell pro- 

 duced by the Chantransia, but as a direct vegetative continuation 

 of the latter. It illustrates what Sachs terms "alternation of 

 axes." % The oospore produced by the Batrachospermum stage, 

 never reproduces itself directly, but on germination, gives origin to 

 a minute cushion of polyhedral cells, which Sirodot terms the 

 prothallus, and without developing further, can reproduce itself by 

 sporules. Sooner or later it generally gives origin to branched 

 filaments which develope into the Chantransia condition, this in 

 turn can produce itself by sporules ; if vegetative development 

 proceeds further, the sexual or Batrachospermum stage results. 



A well-developed apical cell is always present in Floridese, 

 which in the simpler forms is large, cylindrical, and with a rounded 

 anterior end. This mother-cell is divided into two daughter-cells 

 by a straight or slightly curved septum, transverse to the axis of 

 growth, the apical portion growing until it equals its mother-cell 

 in size, when division again takes place in the same manner. 

 When the thallus consists of a single row of superposed cells, the 

 segment, or posterior daughter-cell is at first disc -shaped, the two 



* " Les Batrachospermes, organisation, fonctions, de'veloppement, classifica- 

 tion," Bull. Soc. Bot. Fiance, xxxi. (ISSi). 



t 'Text-Book of Botanv,' second English ed., 1882, p. 228. 

 t Tom. eit. p. 228. 



