360 Mr. Hassall on the Branched Freshwater Conferva. 



scarcely less interesting and important as regards the classi- 

 fication of Conferva? than the former. 



In many species of Conferva?, more especially amongst the 

 branched kinds, there is not only a longitudinal development 

 of the cells, but there is likewise a lateral growth of them, so 

 that if we examine any species in which this law is known to 

 exist, we shall observe, first, that the filaments differ consider- 

 ably in diameter in the same specimen ; secondly, that the 

 largest filaments are near the centre of the specimen ; and 

 thirdly, that the diameter of all the filaments, whether these 

 be near the centre or circumference, gradually decreases from 

 base to apex ; the observation of these three things proving 

 the existence of the law of lateral development of the cells, and 

 also showing it to be in proportion to their age. The propor- 

 tions of a specimen of branched Conferva are therefore, in 

 miniature, those of a tree or shrub. 



I have observed this law of growth to exist in the following 

 Conferva? : in the Vesiculasperms, many Diatomacea, and in 

 Conferva zonata, the filaments of all of which are simple ; in 

 the Batrachiosperms, the genera Draparnaldia and Chceto- 

 phora, in Conferva glomerata, C. crispata, C. flavescens, and 

 in C. (Bgagropila, in all of which the filaments are branched. 

 It has no existence in the Conjugating Conferva?, in many 

 Oscillatorice, in some of the species of the genus Desmidium, 

 and in the genus Bulboch&te, all of which, save the last, have 

 simple filaments, whose diameter does not vary with age, but is 

 the same in the immature and mature condition of the species. 



These laws of the lateral development of cells prevail 

 doubtless likewise amongst the majority of the marine ramose 

 Conferva?, and it is important that it should be kept in view 

 in the framing of genera. 



The reproduction of the branched Conferva?, whether ma- 

 rine or freshwater (for I believe it to be the same in both) is 

 still shrouded in much obscurity, but certainly differs essen- 

 tially, if we except the genus Buldochaete, from that of the Con- 

 ferva? with simple unbranched filaments, the Synspores of 

 M. Decaisne, and the Vesiculasperms ; for in them there is no 

 intermingling or union of the contents of the adjacent cells, 

 either in the same or different filaments, and no formation of 

 a true spore ; but there is, as in the Vesiculasperms, an infla- 

 tion of the reproductive cells, which inflation is produced by 

 an increase in the size of the small sporular granules, some 

 twenty, thirty or more of which are contained within each cell. 

 The determining cause whereby this increase of the granules 

 is produced is at present a mystery, the solution of which is 

 much to be desired. The inflation of the reproductive cells of 



