FINK—THE LICHENS OF MINNESOTA. 133 
filaments. The fungal hyphz frequently lie in contact with the sheath of the algal 
filaments, but there are no haustoria, and the relation of the two symbionts is not so 
close as in most other lichens. The thallus is peculiar in two of the genera in being 
foliose in form and still without cortex, in this respect like crustose thalli. The foliose 
condition here is of course due to the peculiar nature of the algal symbiont, which 
_ quite largely determines the form of the thallus. . 
The apothecia more commonly show a thalloid exciple, but are on the whole more 
nearly biatoroid than those of any family following. The family is, therefore, placed 
near the Lecideaceae, though there is much room for difference of view as to the 
relative position of the present family and several to follow. However, as to spore 
characters some of the families next to follow seem lower than the present one. With 
respect to the spores, the Collemaceae seem nearest to the Pannariaceae. 
SYNECHOBLASTUS Trev. Caratt. Gen. Collem. 2. 1853. 
The thallus is foliose, but is frequently extended above into marginal or submarginal 
rugose lobes which give a cespitose-fruticose appearance, sometimes wholly obscuring 
the horizontal portion even to the center of the thallus. In the higher forms of the 
genus, the thallus is quite expanded, The cortical layers of the thallus are wholly 
absent, nor is there any distinct algal layer. On the other hand, the alge, which 
consist of a species of Nostoc, showing the heterocysts plainly, are scattered throughout 
the entire thallus. The algie occur in chains, which are rather more numerous toward 
the upper surface of the thallus, or not infrequently quite as numerous toward the 
lower sides, The chains of algal cells are easily distinguishable, though possibly on 
the whole hardly so long as in Collema, The color of the thallus is bluish, olivaceous, 
or black, and usually lighter below than'above. The thallus may be attached to the 
substratum by direct adhesion of the lower surface or by rather sparingly developed 
simple rhizoids. 
The apothecia are rather small and are ordinarily developed in all but one of our 
species. The thalloid exciple is commonly present and extends somewhat above the 
disk. The color of the disk is generally brown or brownish black, and it is usually 
flat or slightly convex. The hypothecium is commonly pale or pale brownish, and 
the hymenium pale below and brownish above. The paraphyses are ordinarily 
simple, though branched :orms may be found in all the species. The spores are 
hyaline, from 2 to several-celled, but never muriform. 
We have divided the genus Collema as conceived by Tuckerman, placing in that 
genus those species having more or less muriform spores and in the present one those 
not so divided. There seems to be a gradual evolution of spore characters running 
through the two genera, which are very closely related, The relation of both genera 
to Leptogium is‘also a close one, Collema, as to spore characters at least, seeming to be 
intermediate between the other two. 
A half dozen forms occur in the State. On trees and more rarely on rocks. 
Type species Collema nigrescens (Huds.) Ach. loc. cit. (Synechoblastus nigrescens 
(Huds.) Stizenb.) 
KEY TO THE SPECIES. 
Thallus lobes quite closely attached to the substratum. 
Spores several-celled, long and narrow; apothecia pruinose.. 4a. S. nigrescens leu- 
id copeplus. 
Spores as above; apothecia not pruinose......-.---------- 4. S. nigrescens. 
Thallus lobes not closely attached to the substratum. 
Erect or nearly so. 
Spores 2-celled. 22... -.-..0 25205. 2 5-25 -eeee eee eee L. S. pyenocarpus. 
Spores 4-celled......-.. 05-50-55 +--+ +2502 e terete eee 2. S. cyrtaspis. 
Ascending. 
Spores 4 to 6-celled, rather short and wide......--.--- 3. S. flaccidus. 
Spores 4 to 8-celled, longer and narrower......------- 5. S. ryssoleus. 
