'92 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Schmidt's Atlas der Diatomaceen-Kunde. — The latest part pub- 

 lished of this fine work, Heft 55, consists of the four plates 217-220, 

 with accompanjing letter-press, and is entirely devoted to the genus 

 Mhabdonema. 



Cladophors .* — Herr F. Brand gives a detailed account of a variety 

 of observations on the European species of Cladophora. Among the 

 more important results are the following. There is much greater 

 variation in the characters of the species than has hitherto been sup- 

 posed, and the diagnoses must be enlarged. The relative length of cells 

 •of Cladophora is, in particular, so variable that it can only be used to a 

 very limited extent, and never by itself, for the discrimination of species. 

 The statement that all species of Cladophora form, when young, attached 

 tufts, is probably not true for C. fracta, or only in a very temporary 

 manner. The branch almost always springs from the upper part of the 

 lateral wall of the mother-cell (rarely from the lateral wall of the next 

 •cell). The first point to note in determining the position of a species 

 of Eucladophora is whether it has primary (then always strong) basal 

 organs of attachment. Species belonging to this class usually form 

 zoospores ; the free-swimming species are mostly propagated by resting 

 spores. All the European species of Cladophora described by Eabenhorst, 

 except the iEgagropilae, must be regarded as varieties, forms, or con- 

 ditions of C. fracta or glomcrata. The protoplasm of Cladophora has 

 an especial affinity for methyl-green-acetic-acid. 



Fungi. 



Influence of Nutrition on the Respiration of Fungi.f — As the re- 

 isult of a series of experiments, chiefly on Agaricus campestris and Mucor 

 Mucedo, M. A. Fleroff finds these two fungi to be representatives of two 

 different types. In Mucor the withdrawal of a nutrient substratum 

 materially depresses respiration, while the supply of nutriment greatly 

 increases it ; with deficient nutrition the formation of spores is at once 

 •set up. With the mushroom, on the contrary, the development of the 

 receptacle is hardly influenced by the supply or withdrawal of nutrition, 

 the fungus itself containing sufficient food-material for its formation. 

 The respiration of the niushroorn is in general very feeble, 3*2 mgrm. of 

 C0 2 per 1 hour for 1 grm. of dried substance ; while that of Mucor 

 Mucedo amounts to 28*8 mgrm. of C0 2 for the same time. 



Compound Oosphere of Albugo Bliti.f — Mr. F. L. Stevens describes 

 tihe remarkable phenomena connected with the process of fertilisation 

 occurring in Cystopus (Albugo*) Bliti, belonging to the Phycomycetes, 

 parasitic on species of Amaranthus in the United States. The mature 

 oosphere contains a large number (as many as 300) of female nuclei, 

 and these are impregnated by an > qjial number of male nuclei introduced 

 into the oogone through the antheridial tube ; this fusion in pairs 

 resulting in the production of about 100 impregnated oospheres. 



When the oogone is cut otf from the parent hypha, it contains from 

 250 to 300 nuclei, which enlarge, and divide mitotically. The antherid, 



* Bot. Centralbl., lxxix. (1899) pp. 145-52, 177-86, 209-21, 287-311 (3 pis.). 



t Tom. cit., pp. 282-7. 



X Bot. Gazette, xxviii. (1899) pp. 149-76, 225-45 (5 pis.). 



