50 PROCEEDINGS OF THE AMERICAN ACADEMY 



CoUema rnicrophyllum, Ach. 



Synechoblastus conglumeratus^ Krb. = CoUema conglomeratum, Hoffm. 



Collema multijidum, (Scop.) Kib. 



" pulposum, (Bern.) Nyl. 



" nigrescens, (Huds.) Ach. 



The work for the future must be the careful examination of all 

 forms of gelatinous lichens, and the accurate observation of all types 

 of reproduction found to occur in the group. 



Summary of Results. 



1. My investigations upon the Collemaceous genera Leptogium and 

 Collema, under which latter genus are to be included the forms de- 

 scribed by Stahl under the name Physma, Mass., are entirely confirm- 

 atory of the results arrived at by Stahl in his investigations upon those 

 groups. There exist in the Collemaceoe at least two modifications of 

 a sexual type of reproduction, one monoclinic, of which Collema cha- 

 lazanum, Ach., is a typical example, the other diclinic, exemplified by 

 Leptogium myochroum, (Ehrh., Schaer.) Tuck., and Collema nigrescens, 

 (Huds.) Ach. 



2. The genus Hydrothyria, represented by H. venosa Russ., can- 

 not, as heretofore, be considered as typically Collemaceous, but is to 

 be regarded as transitional in its character, and related to the genera 

 Peltigera and Pannaria, between which it forms a more or less defi- 

 nite link. 



3. In the groups of typically heteromeric lichens more nearly re- 

 lated structurally to the Collemaceae, as well as in the transitional 

 forms represented by Pannaria, Heppia, and Hydrothyria, there exists, 

 so far as I have seen, no visible evidence of any sexual form of repro- 

 duction. The development of the fruit is a purely vegetative process 

 analogous to that seen in many Ascomycetous fungi.* 



4. In all such lichens, as far as my observation goes, there exists 

 at no stage in the development of the fruit any differentiation of the 

 hyphae into an ascogenous system and an enveloping system distinct 

 from it.* Both asci and paraphyses arise from one and the same sys- 

 tem of hyphae, and with respect to their origin exhibit the closest 



* Pleospora. Miyabe, " On the Life-History of Macrosporium parasiticum, 

 ThUm.," Annals of Eotany, Vol. III. No. IX. pp. 10, 24. 



Claviceps, Epichloe, and Nectria. De Bary, Comparative Morphology and 

 Biology of the Fungi, Mycetozoa, and Bacteria, English translation, p. 200. 



Sphyridiiim, (^ladonia, and Rajomyces. Krabbe, " Entwicklung, Sprossung 

 und Theilung einiger Flechtenapothecien," Botanische Zeitung, 1882. 



