ZOOLOGY AND BOTANY, MICKOSGOPY, ETC. 213 



slight colour changes ; clamp connexions are abundant, and mycelial 

 stands are formed. The basidiocarps of Cyathus originate from strands, 

 while those of Grucilmlum may arise from mycelial strands, dense mats 

 of hypha3, or from the interior of old peridioles. A. L. S. 



Lichens. 



Thallus der Kalkflechten. — '^.BkQBM.k^^is {Nova Acta Ahh. Leop.- 

 Carol. Deutsch. AJmd. Naturf., 1919, 105, 1-80, 4 pis.)- In this paper 

 the author records results of his examination of a series of lichens living 

 on or in limestone. One of these, Verrucaria parmigera, is associated 

 with PJeurococcus algae, the other five species with Chroohpus. Among 

 the lichens of the latter group the algal threads penetrate along with the 

 lichen hypha deep down into the limestone in GyaUcta cupularis, G. 

 cucapsis, and Sagedia hyssophila. In Arthopyrenia saxkola and Acro- 

 cordia comidea the thallus is more superficial and the penetration is 

 not so great. Bachmann describes both algse and hyphse, their form, 

 etc., and their relation to each other. The occurrence of fat-cells is 

 noted. In other endolithic species {Petractis clausa and Xanthopyrenia 

 {Arthopyrenia) tichotJ tec io ides) he demonstrates the presence of Glceocapsa 

 (Xanthocapsa) gonidia. A. L. S. 



Microscopical Structure of Lichens. — Egbert Paulson {Journ. 

 Quek. Micro. Glub, 1920, 14, 8 pp., 1 pL). R. Paulson gives a short 

 account of the general structure of lichens. He dwells more particularly 

 on the theories of parasitism and symbiosis. He himself brings forward 

 new proof of the symbiotic nature of the thallus in the condition of 

 the gonidia or green cells. These are entirely healthy and normal, 

 and at certain seasons they multiply very actively by sporulation within 

 the mother-cell. This condition of sporulation is found in many of our 

 familiar lichens, the gonidium being a species of Chlorella. In other 

 lichens are to be found other gonidia, but apparently all are healthy and 

 capable of increase. A. L. S. 



The Lichen as Transmigrant. — ii. H. Church {Journ. Bot., 1921, 

 59,- 7-13, 40-6). Church presents a further contribution on the 

 origin of the lichen plant. He gives his views on the development of 

 the thallus from deteriorating green algte, saved from ultimate decay by 

 the intrusion into their tissues of minute green alg^e. He traces the 

 development of the ascocarp, the ascus having been elaborated in the 

 first place from a unilocular sporangium. He contrasts the perithecia 

 of lichens with the cystocarps of the Floridete. He considers that the 

 small ascocarps scattered over the thallus, as in lichens, is more primi- 

 tive than the large fruiting body of the Pezizee, and he notes in lichens 

 the suggestion of vestigial sextml organs, such as the trichogyne, etc., 

 though he considers that there is no direct connexion between lichens 

 and Floride^e. He discusses the whole question of symbiosis in the 

 lichen and in other organisms. The lichen habit, he considers, could 

 not have been evolved in the open sea, but must be the product of sub- 

 aerial and transmigrant conditions. The stages of association are 

 sketched as a sequence of biological factors — {1) Failure of oxygen 



