OF ARTS AND SCIENCES. 47 



of the transformation of the spermogonium into an apotheciuni, for 

 the reason that in the specimens examined by me the characteristic 

 structure of the spermogonia had almost entirely disappeared, and 

 nothing but rather advanced stages of apothecial development were 

 to be found. In the case of PJnjsma Mulleri, however, there could 

 be seen, projecting from the sides of the upper part of the young 

 apothecia, traces of sterigmata. (Plate VII. Fig. 37.) I found that 

 treatment with potassic hydrate, a solution of iodine and potassic 

 iodide, and subsequently with dilute nitric acid, gave the best re- 

 sults in these and the following species, in bringing out the course 

 and structure of both hyphoe and trichogynes, the iodine coloring them 

 a deep brown, while the nitric acid, without destroying this colora- 

 tion, partially dissolves the investing gelatinous sheaths of the algae, 

 enabling us to see the hyphae with much more distinctness. 



The peculiar process of ascus formation at the base of the spermo- 

 gonium, as seen by Stahl and hinted at in my own observations, was 

 established by Stahl as characteristic of the genus Physma, Mass., rep- 

 resented by the species P. franconicum, P. compactum, and P. myrio- 

 coccum. On other than carpologic grounds, however, recent writers 

 have placed these species in the genus Collema, the first and second 

 under the name C. chalazanum^ the third as C. myriococcum, and even 

 this form, it is stated, may prove to be identical with C. chalazanum.* 

 Of the two remaining species of this old genus Physma,t P' sanguino- 

 lentum, Krmph., and P. 3Iulleri, Hepp, the former has been described 

 by Koerber, but the description is not sufficiently definite to place the 

 species with any certainty, although Koerber states that it resembles 

 Heppia adglutinata^ (Krmph.) Mass. \^H. Despreauxii, (Mont.) Tuck.]. 

 Specimens of H. Miilleri, Hepp, exist in the Hepp herbarium,^ and I 

 have been fortunate enough to be enabled to examine and compare the 

 specimens. It is undoubtedly a Collema, very closely resembling in 

 liabit C. myriococcum, (Ach.) Arn., as well as C. chalazanum, Ach. 

 The thalline structure agrees rather more closely with my specimens 

 of the latter, while the spores are considerably smaller than the meas- 

 urements given by Nylander for C chalazanum, and agree with the 

 authentic spore measurements of C. myriococcum. The spores of 

 P. MUlleri measure 9.4—11.3 yu, X 7.5-9 yu, are nniseriate in the asci 

 and round-elliptical in shape, thus agreeing exactly with the spores of 

 C. myriococcum. We may then with considerable certainty consider 



* Tuckerman, Synopsis of Nortli American Lichens, p. 143. 



t Koerber, Parerga Liclienum, p. 409. 



X Lich. Helvet. Exsic. Schaerer and Hepp, No. 933. 



