INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 1025 



the continuous tubes are always enclosed by an evident membrane, and 

 the deposit always consists of a number of concentric layers, which 

 are again sejiarated by membranous division-walls. Isolated streaks 

 or warts indicate the commencement of the deposit. On treatment 

 with potassium ferrocyanide, with addition of hydrochloric acid, the 

 iron is dissolved, and Prussian blue formed. The deposits first appear 

 as minute dots between the inner and outer membranes, which soon 

 unite ; or the formation begins between the layers of the septa of two 

 cells, forces itself outwards, and spreads in the form of a sheatli in 

 both directions of the superficies of the cell, raising up the outermost 

 layer. The formation of several concentric layers may be the result 

 of a repeated raising-up of successive layers of cell-wall. 



Kiitzing has described these incrusted confervae as Psichohormium 

 (according to Hanstein Psichormium), but Hanstein does not consider 

 the genus one that can be retained, and proposes to combine the species 

 Psichormium glohuliferiim, didans, approximatum, incBquale, and fus- 

 cescens under the name Conferva martialis, imtil a more full investiga- 

 tion has been made of their mode of reproduction. Hanstein states 

 that propagation has been efiected by disintegration of the cells. 

 Besides the iron hydrate there is also abundance of calcium carbonate 

 lying loose on the surface of the filaments or between them, which, 

 however, does not form an organic envelope, and is similar to that 

 which occurs in CEclogonium ; it is only attached externally. Klitziug's 

 figures of P. antliare, cinereum, puhescens, &c., appear to represent such 

 incrustations. 



Hanstein explains the phenomenon by supposing that these confervte, 

 when in active growth and greedy for carbonic acid, take up the iron 

 dissolved by the carbonic acid in the water, deprive the carbonate of 

 its carbonic acid, and deposit beneath its outermost layer of cell-wall 

 the iron which has been oxidized by the nascent oxygen, while the 

 calcium carbonate, deprived of one atom of carbonic acid, usually 

 remains external, but sometimes in the internal spaces. 



Germination of the Zoospores of (Edogonium.* — Wille confirms 

 in all essential points Poulsen's description, adding a few new observa- 

 tions. The ring is formed at the apex of the cells, and is drawn out 

 upwards in a longitudinal direction. The red eye-spot can be made 

 out almost until the first division takes place. A large number of 

 the germinating plants do not multiply by division, but again form 

 zoospores, which separate and have a long, extended, but unbranchcd 

 or only slightly branched root-portion. Those whicli divide are 

 cither firmly seated or have a unieh-branchcd attachment-disk, which 

 is formed when the gi'owing root-portion meets with an impediment 

 by which gi-owth in length is prevented. The j)urietal protoplasm 

 then continues in an active state, causing a lateral cximnsion of tlio 

 radicular extremity, and frequently forming new branches, altliough 

 growth usually ceases. The formation of cellulose ajjpears to be pro- 

 portionate to the mass of the parietal protoplasm. 



* 'Christianiu Vidcnsk. Forhandl.,' 1880. Sec ' Bot. Ccutralbl.,' i. (1880) 

 p. 581. 



