ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 223 



All of these he considered had originated from spores ; some of the 

 mycelial strands had already come into contact with algre, and the 

 thallus formation had begun. 



Kajanus next takes up the question of variation in structure, and 

 discusses the character and origin of the differences in structure. He 

 discusses the formation of isidia and soredia, both of which are due, he 

 considers, to an excess of moisture causing increased gonidial activity. 

 He described the occurrence of these two structures in a number of 

 hchens as an entirely biological phenomenon. 



Monograph of the genus Solorina.* — Hue now publishes a com- 

 plete account of the eleven species of this genus. He divides them into 

 three sections. (1) Pleurothea, including one species, Solorina crocm, in 

 which the gonidial layer is composed of two algte, one Chlorophyceae, 

 the other Phycochromace^e ; (2) Solorinina, in which the algfe belong 

 to the Phycochromaceae alone ; and (3) Eu-Solorina, in which the algte 

 are bright green Chlorophyceas. The first section, Fburothea,\TpToxe& 

 that lichen hyphfe can associate with more than one kind of alga. 



Lichen Ecology in Thuringia. — G. Lettau continues his study of 

 this subject. He notes that often through cultivation the xerophilous 

 crustaceous forms are destroyed, to be later replaced by mosses and 

 Cladoiiise ; many rock faces, however, have remained unchanged for long 

 periods. In the woods the frequent use of lime on the trees and the 

 soil has cleared out many species ; the thinning of the woods and the 

 drying up of the soil have also aided in the work of extermination. 

 Forest culture is answerable for the disappearance of such species as 

 Stenocybe major, Loharia am^iUssima, Usnea longissima, U. ceraiina, and 

 Ochrolechia tartarea. Species that in damp woods grew high up on the 

 trunks of the trees, now grow only in the lower parts. Lists are given 

 of the species that have persisted in the woods in spite of changed con- 

 ditions. 



The author next discusses the flora of the lowland as contrasted with 

 that in upland or alpine districts. They are common to both regions, 

 though several that are frequent in the one are more sparse in the others. 

 It is especially noticeable among Cryptogams generally, that alpine forms 

 occur sporadically in the lowlands. 



As to the horizontal distribution of species, he finds that the district 

 is comparable with the middle and south German high lands or " sub- 

 alpine mountains." Mediterranean forms that are found in west German 

 Upper Rhine country are absent in Thuringia. They are to be found in 

 the south-west as far as Hesse, Westphalia, and the Main, but do not 

 appear in the region examined. Lists are given of lichens characteristic 

 of the various distiicts and substrata. 



Biology of Lichens and Lichen Fungi. | — F. Tobler takes up the 

 question of lichen parasites and their relation to the tissues of the host- 



» M6m. Soc. Sci. Nat. Math. Cherbourg, xxviii. (1911) ,p, 1-56. See also Bot. 

 CentralbL, ciix. (1912) pp. 24-5. 

 + Hedwigia, li. (1311) pp. 209-20. 

 X Pringsh. Jahrb. Wiss. Bot., xlix. (1911) pp. 389-417 (1 pi,). 



