46 PROCEEDINGS OF THE AMERICAN ACADEMY 



ness of Stahl's account, emphasized as it is by numerous figures, has 

 seemed to preclude the necessity for further confirmation. It was not 

 so with regard to the heteromeric lichens. Neither Stahl's observa- 

 tions on this point, nor those of his followers, seemed to me sufficiently 

 definite to warrant their acceptation without further confirmation. I 

 therefore attempted this task in those groups of lichens which exhibit 

 the most marked affinities to the Collemaceae. But failing to discover 

 there the points which I had been led to expect might well be found, 

 I hesitated about accepting without further proof even the clearness 

 of Stahl's statements iu regard to the Collemaceaj. I have therefore 

 been led to attempt a confirmation of these statements satisfactory to 

 myself, with the following result. I have examined specimens of 

 Physma Mulleri, Hepp. {^Collema myrtococcum, Ach.) ; Collema chala- 

 zanum., Ach. {Lemj)holemma compactum, Krb., Physma compactum, 

 Mass.); Collema pulposum, Ach. ; Collema nigrescens, (Iluds.) Ach.; 

 and Leptogium myochroum, (Ehrh., Schaer.) Tuck. {L. sattirninum, 

 Nyl., 3Iallotium tomentosum, Krb.) ; and although I have not carried 

 my observations as far as did Stahl, I have established in all cases 

 the essential point, — the existence within the thallus of a coiled 

 ascogonium prolonged upwards in the form of a multicellular thread, 

 the trichogyne, whose tip appears above the surface of the thallus. 



Collema chalazanum, Ach. 



In sections through a young apothecium of this lichen, identical ac- 

 cording to Nylander with P/tysma compactuni, Mass., it is by no means 

 difficult to detect, generally close to the denser investing tissue of the 

 apothecium near the base, one or more structures identical with those 

 figured and described in this species by Stahl as trichogynes. (Plate 

 VII. Fig. 36.) They are delicate septate threads no larger than the 

 ordinary fungus-hypha^, but at once distinguishable from them by the 

 thickening of the septa, more marked near the surface of the thallus 

 than below. I have never seen more than four such hyphce in one 

 section, and generally there are but one or two, nor in a thin section 

 should we expect to find more than this, since, according to Stahl, at the 

 base of one spermogonium arise only six or eight trichogynes in all. 

 Inasmuch as these peculiar hypha) originate in a system of larger cells 

 occupying the base of the young fruit, and reach the surface only at 

 some distance from it, it is very rarely that the plane of the section 

 corresponds exactly to that of a trichogyne, thus making it possible 

 to trace the continuous course of the latter from its point of origin 

 up to the projecting tip. I was also unable to follow the process 



