1012 SUMMARY OJ' CURRENT RESEARCHES RELATING TO 



2. Mi/corjifne cerrinn on species of Peziza, is tlio Jli/poniiu'es ccrvhuts 

 of Tnlasno. 3. Sphseronema Leotiarum en Leotia luhriea. This is 

 probably the pycnidial form of Hijpomyccs Leatiannn Fayod. 



Protophyta. 



Cellular Envelope of the Filamentous Nostocacese. * — M. M. 



Gomont imblishcs further details of liis investigations on this subject. 

 The true eell-nienibrane he finds to be always present at all times of the 

 life of the plant, though it is always very thin. The enveloping sheath, 

 on the other hand, is gelatinous or membranous, and is composed of 

 parallel lamella? or of co its inclosed one within another. 



As regards the development of these structures in the different 

 families of Filamentous Nostocacea; : — in the Oscillariacea) the cellular 

 membrane frequently takes the form of a cap, varying in form in the 

 dilFerent species, but constant in each. That this cap does not belong to 

 the mucilaginous sheath, as was supposed by Borzi,| is shown by the 

 fact that it is frequently formed within the prolonged tube of the latter 

 when the filament is broken. This cap was observed in many species 

 belonging to different genera, fresh-water, saline, and terrestrial ; it is 

 especially well developed in Oscillaria antliaria. 



In the Nostocea) the presence of the cellular membrane can only be 

 demonstrated by the use of reagents. This is also the case in the 

 Scytonemeae and Stigonemefe. In all cases the heterocysts appear also 

 to be provided with this membrane. 



In the Kivulariacca) the terminal hyaline bristle is in perfect con- 

 tinuity with the rest of the cellular membrane ; it is distinguished 

 only by having fewer transverse septa, and by the entire absence of 

 granular protoplasm. 



The spores of the Nostocacea? always possess two coats, an exosporc 

 and an endiispore, the former of which is again ctimposed of two distinct 

 layers, the outer one being very frequently warty or otherwise marked. 

 These spores are always the result of the encysting of ordinary vegetative 

 cells. 



Chlorothecium.} — Sig. A. Borzi describes several points not hitherto 

 known in the life-history of Chlorothecium Piroitse, belonging to tlie 

 Sciadiacca3. The nearest approach to its structure is presented by 3Iis- 

 chococcHS. It was found csjiecially growing on Marsilea and Chaetomorphn, 

 in palmelliform colonies of cells with a length of 14-40, and a breadth 

 of 10-18 /x, with an ultimately thick and firm cell-wall. These cells 

 develope into zoosjwrangia without any alteration of their in-imitive 

 form ; from each cell there usually escape two or four, rarely only a 

 single zoospore, from 8-5 fx in length, and provided with a single cilium 

 and a consjiicuous eye-spot. Conjugation takes place between these 

 zoosj^ores or zoogametes by gradual fusion. The mature zygospore has 

 a diameter of 7-10 /u,, and a moderately thick but transparent membrane. 

 After hibernating the contents of the zygospore breaks up into two 

 masses, each of which escapes in the form of a zoospore, so that the 

 zygospore is itself a zoosporangium. From these zoospores are again 



* Bull. Sue. Bot. France, xxxv. (18S8) pp. 204-36 (2 pis.). Cf. this Journal, 

 ante, p. 632. t 'See this Joiurnal, 1887, p. 448. 



; Malpi-hia. ii. (1888) pp. 250-0. Cf. tliis Journal, ante, p. 6:h2. 



