350 SUMMARY OF CURRENT RESEARCHES RELATING TO 



petioles near the base, and the leaf dies off. On the diseased petioles 

 there develops also Coniothyrium Hellehori, followed by other fungi and 

 bacteria which complete the work of destruction. A. L. S. 



liicliens. 



Lichen Flora and Lichen Vegetation of Iceland.— Olaf Gall0e 

 {The Botany of Iceland, 1919-20, 2, 1, 1-248). In the introduction the 

 author gives an account of work done by previous collectors. This is 

 followed by a critical examination of tlie methods of classification and 

 by the lists of lichens, most of them seen and collected by himself. In 

 these lists he notifies the occurrence of the lichens in (xreenland and 

 in Great Britain. Gall0e discusses the means of dispersal and distri- 

 bution, with special reference to the conditions that prevail in Iceland ; 

 he concludes that wind is there the chief agent in scattering spores or 

 portions of the lichen thallus. Tlie special ecology of Iceland lichens 

 occupies a good deal of his paper. There are few trees, and the bark 

 lichens are "mainly those growing on old birch trunks. Rock and soil 

 lichens are numerous, but CTa]l0e decides that abundant growth is 

 inhibited by the extreme cold of such a northern region. 



A. LoRRAix Smith. 



Hints for Lichen Studies. — Albert C. Herre {Bryoloyist, 1920, 

 23, 26-7). Herre deplores the small number of people that interest 

 themselves in the study of lichens, seeing the plants are more or less 

 abundant everywhere. He concludes that it is the lack of manuals that 

 has hindered students. He suggests as an interesting field of study tlie 

 observation of yearly growth in definite species and individuals. He 

 also adds observations on the meaning of the lichen plant, which is 

 largely a physiological species, but shows constant heredity. A. L. S. 



Mycetozoa. 



Critical Study of the Slime-Moulds of Ontario.— Mary E. Currie 

 {Trans. Roy. Ganad. Inst, 1920, 12, 247-^08, ?> pis.). The majority of 

 the mycetozoa recorded in this paper were collected in the Lake Ontario 

 region ; a few were from other parts of Ontario. The writer enumerates 

 29 genera and 117 species and varieties. Of these :i species and 

 2 varieties are new to North America. Interesting biological and de- 

 scriptive notes are given, along with the exact localities and substrata. 



A. LoRRAiN Smith. 



Mycetozoa and Disease. — J. Jackson Clarke {Protozoa and 

 Disease, 1920, 5, 1-133, 1 pL, 46 figs ; London : Balliere, Tindall and 

 Gox). The author claims to have proved the occurrence of mycetozoa 

 in cancer. He gives a history of mycetozoa, more especially of their 

 development as observed in cultures, and adds his own observations, 

 which are mainly concerned with the culture of Didymiwn difforme. He 

 then describes cultures of very similar organisms that developed from 

 cancer. Careful figures of the organisms in both cases are placed side 

 by side. He gives arguments and reasons in support of his facts. He 

 contrasts, for instance, in a striking figure the formation of capillitiuni 

 fibres in tubers and those in a mycetozoon {Comatricha nigra), both 

 examples taken from his own cultures. A. L. S. 



