790 SUMMABY OF CURRENT RESEARCHES RELATING TO 



is of small consequence to the lichen, which derives no nutriment, but 

 merely suj^port therefrom. Nor does the author agree that the 

 chemical composition of the thallus varies according to the nature of 

 the substrata. 



Hymenolichenes.* — This section of lichens was established by 

 Mattirolo j from the genus Cora, and depends on the symbiosis of an 

 alga with a fungus belonging to the class of Hymenomycetes. F. 

 Johow has critically examined the group in its native country of 

 Venezuela and the West Indies, and includes in it the four following 

 genera : — Cora, BMpidonema, Dictyonema, and Laudatea gen. nov. 

 The first three genera must be regarded, from their habit and the 

 lamination of their thallus, as heteromerous foliaceous lichens, but 

 differing from all other genera in the entire absence of a solid cortex 

 and in the unusually complete investment of the algsB which perform 

 the function of gonidia. Laudatea is distinguished by its peculiar 

 CEespitose habit, and by the segmentation of the thallus connected 

 with it into a saprophytic mycelium and green stems composed of 

 bundles of gonidia invested by fungus-hyphse. 



The systematic position of the Hymenolichenes is among the 

 Thelephorea, and in near relationship to Thelephora, Corticium, and 

 Hypochnus. The only organs of reproduction which they possess are 

 sporiferous basidia growing on the under side of unilateral pilei, or on 

 crustaceous receptacles (^Laudatea). Nylander's statement of the 

 presence in Cora of apothecia has not been confirmed. The saprophytic 

 inycelium and crustaceous receptacle of Laudatea find their analogue 

 in numerous species of Thelephora and Corticium, The green foliaceous 

 thallus of Cora is homologous to the receptacle of Thelephora. 



Algae. 



Fresh-water Phseospore.l — Under the name Lithoderma fontanum, 

 E. Flahault describes a fresh-water phgeosporous alga from the neigh- 

 bourhood of Montpellier. It agrees with other species of the genus 

 in having the zoosporangia naked and superficial. The thallus is 

 closely adherent to the substratum, recalling that of Melohesia or 

 Coleochcete. The zoospores are ovoid, unequilateral, with a red eye- 

 spot and two unequal cilia inserted on the concave side of the zoospore, 

 and directed one forwards, the other backwards. They germinate 

 directly, without conjugation. 



Nostoc.§ — C. Flahault has had the opportunity of examining the 

 structure of the rare Nostoc flagelliforme, growing in the neighbour- 

 hood of Montpellier, described by Berkeley and hitherto known only 

 from Texas. He regards it as identical with the Nematonostoc 

 rhizomorphoides of Nylander, which genus must therefore disappear. 

 Spores were not observed, but hormogonia frequently. Nostoc flagelU- 



* SB. K. Preuss. Akad. Wiss. Berlin, 1884 pp. 113-28 ; also Pringsheim's 

 Jahrb. f. Wiss. Bot., xv. (1884) pp. 361-409 (5 pis.), 

 t See this Journal, ii. (1882) p. 542. 

 % Comptes Kendus, xcviii. (1884) pp. 1389-91. 

 § Bull. See. Bot. France, xxx. (1883) pp. 89-96 (1 pi.). 



