OF ARTS AND SCIENCES. 29 



in none of the many sections examined by me has any trace of such 

 an organ a{)peare(l. 



"We next find that the upper lialf of the young apothecium has dis- 

 appeared, presenting the appearance of having been torn apart by the 

 cessation of growth below, and from the upper part of the cavity thus 

 formed are seen suspended the remnants of the liyphic. The lower, 

 flattened surface of the cavity is now seen to be composed of a dense 

 layer of young paraphyses. The gonidial layer has been raised up 

 over the young apothecium, only traces of it appearing below in the 

 shape of a few separate algae, or small groups of them, which have been 

 embedded in the lower part of the young apothecium and remain there. 

 The first evidence of the coming exposure of the hymenium, is seen in 

 the loosening of a broad, wedge-shaped portion of the algal layer and 

 the cortex immediately above the young hymenium, as though by the 

 expansion of the latter it were to be thrown off bodily. The later 

 development is like that described in the case of S. anthraspis. Be- 

 fore the cortex is ruptured, and the hymenium exposed, the asci begin 

 to appear, at first sparsely throughout the hymenium, but soon in 

 greater numbers ; the tissue covering the disk is thrown off, and the 

 hymenium, surrounded by a thick, thalline exciple, appears on the sur- 

 face. To determine the origin of asci and paraphyses the same method 

 of treatment may be employed as before ; and here again the asci alone 

 are colored blue, the coloration not extending into the hymenium. 

 No more than in the case of S. anthraspis is it possible to find two 

 separate systems of hyphce in the subhymenial tissue. The figures 

 (Plate I. Figs. 4-G) show a variety of forms by which the relation 

 between the asci and paraphyses is established. 



Nephroma tomentosum, (Hoffm.) Krb. 



The genus Nephroma, as already pointed out by Schwendener* and 

 also by Tulasue,t forms a connecting link between the genera Sticta 

 and Peltigera. To quote from the author first named, " Whereas the 

 peltate, borderless apothecia emphasize the affinity of this genus (Ne- 

 phroma) to Peltigera and Solorina, the anatomical structure of the 

 thallus presents such a perfect agreement with that of Sticta, that it is 

 impossible to find a single characteristic which cannot also be found in 

 one or another species of the circle of Sticta forms." % 



* Scliwendener, Na<;eli's Beitrage, Heft III. p. 1G6. 

 t Tulasne, Mem. Lich., pp. 20 and 145. 

 t Schwendener, loc. cit., p. 173. 



