388 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Verrucaria margacea.* — Ethel M. Poulton writes a descriptive and 

 systematic account of a species of lichen determined by her as Verrucaria 

 margacea. The authorities quoted and followed by her are of somewhat 

 old date, and no authentic specimens seem to have been examined. 

 The lichen dealt with occurs in great abundance in the streams of 

 Cannock Chase, Staffordshire. When young it is pale-green, but be- 

 comes dark olive-green or almost black when older. The structure of 

 the thallus is compact and pseudo-parenchymatous, and " uniform in 

 structure throughout the whole thallus." The spores are at first uni- 

 locular, later they become bilocular, and finally quadrilocular. They 

 may germinate in any of these conditions. The author concludes from 

 his observations that spore-characters of lichens are not always reliable 

 as a basis of classification unless the complete life-history of the organism 

 is followed out. The spores of her V. margacea are rather minute struc- 

 tures, measuring when in the ascus 12-16 x 5-7 /x ; later they may 

 increase to 21-24 x 9-10 /x. 



Mycetozoa. 



(By A. Loreain Smith, F.L.S.) 



Snow Species of Mycetozoa.f — Ch. Meylan finds that, though 

 Mycetozoa are generally cosmopolitan, there are certain species influenced 

 by altitude and by the presence of snow. He enumerates a number of 

 such species that are constantly to be found in spring on grass and on 

 sticks as the snow recedes. These species are abundont above 1100 in., 

 but are never found in any other locality. It seems evident that the 

 presence of snow — that is an extreme degree of cold — is necessary for 

 their development ; and it was only by carefully removing the snow that 

 Meylan succeeded in discovering the plasmodium in several instances. 

 The time of their appearance varies considerably according to the 

 weather conditions of the spring. Generally, Physarum vernum appears 

 first. Development is most abundant in a warm season. A dry east 

 wind interferes with the growth of the sporangia and induces various 

 abnormalities of form- It is generally the presence or absence of lime 

 that is affected by these weather conditions. Meylan adds detailed 

 descriptions and critical notes of the species which he considers ex- 

 clusively confined to the snow-line. 



Formation of the Capiilitium in certain Myxomycetes.J — R. A. 

 Harper and B. 0. Dodge have studied this subject in the genera Trickia 

 and Hemitricltia, in both of which the capillitia are provided with spirals. 

 According to their observations these threads arise from vacuoles which 

 appear in regular rows. The cytoplasm immediately surrounding these 

 vacuoles becomes very dense, with many fibrils, more or less radiately 



* Ann. of Bot., xxviii. (1914) pp. 241-9 (2 pis.). 

 f Bull. Soc. Vaud. Sci. Nat., 1. (1914) pp. 1-14. 

 % Ann. of Bot., xxviii. (1914) pp. 1-18 (2 pis.). 



