836 SUMMARY OF CURRENT RESEARCHES RELATING TO 



latter peculiarity, which hitherto has not heen met with among 

 the Cryptophycese, indicates in Mazcea a degree of specialization 

 of the parts of the trichome greater than that in any other 

 genus of Stigonemacese, in fact it represents the highest develop- 

 ment in the group. Now that in this genus and in Capsosira 

 Brehissonii ( = Stigonema zonotrichioides N or dst.), Stigonemacese have 

 rivularioid representatives, it may be noted that ScytonemaceaB is 

 the only tribe in which this type is wanting. 



Resting-spores of Conferva.* — Eesting-spores have already been 

 observed by a large number of inquirers in various Confervaceae ; first 

 of all in a Conferva first discovered and figured by Itzigsohn, and de- 

 scribed by him as Psichohormium uliginosum ; and again, by Pringsheim, 

 Famintzin, Cornu, and Rosenvinge, in the genera TJloihrix and 

 Conferva ; and they are now found to be present in the whole genus 

 Conferva (L.) Wille. N. Wille now adds to these contributions his 

 observations on the manner of forming these resting-spores. 



In Conferva Wittroclrii n. sp. the spore-formation is thus carried on. 

 The chlorophyllaceous contents contract and become rounded. The 

 colouring matter collects principally in the ends of the cells, so that 

 the substance in the middle appears nearly colourless ; but after the 

 contraction of the cell-contents the chlorophyllaceous portions of the 

 protoplasm draw nearer together, until at last they coalesce and form 

 a round or elliptical body within the mother-cell ; they then begin to 

 surround themselves with a membrane, which later consists of two 

 distinct layers. The spores are generally set free by the filaments 

 resolving themselves into H-shaped cells (in which the cell-wall of 

 each cell has a transverse fissure in the middle of the transverse 

 walls) ; the spores then fall out. Sometimes they escape by the cell- 

 walls becoming converted into mucilage, their layers becoming gradu- 

 ally indistinguishable. On first germinating, the size of the spores 

 increases, as the result of which the outer membrane bursts. The 

 outer membrane consists of two pieces with pointed ends, one being 

 much larger than the other, and covering it like the lid of a box. 

 Afterwards, through the expansion of the inner membrane, the smaller 

 piece of the outer membrane gives way, and the inner membrane 

 grows through the aperture thus formed in the form of a tube. 

 The development was not followed further, but the writer considers 

 it probable that zoospores are first formed from the resting-spores. 



The development in Conferva stagnorum Ktz. is of precisely the 

 same character ; but here the spores are mostly freed through the 

 conversion into mucilage of the cell- walls. The germination proceeds 

 either as in C. Wittrockii, or transverse walls appear in the elon- 

 gated resting-spores whose outer membrane is not burst, and the 

 young filaments are thus formed. In germination, a sort of organ of 

 attachment is formed by an excretion of mucilage in the pointed end 

 of the spore ; or perhaps the mucilage is a local transformation of the 

 outer membrane. In one case the author observed this sort of cell- 



* Ofversigt af Kongl. Vetensk.-Akad. Forhandl., xxxviii. (1 881), 26 pp. (2 pis.). 

 See Eot. Centralbl., xi. (1882) p. 113. 



