The Origin and Development of the Apotheciiun etc. 401 
The hymenium is at first concave, but as more asci and paraphyses 
are formed, it becomes flattened and even convex. A sheath of para- 
physes forms a thin pseudo-parenchyma layer, the proper exciple, which 
separates the fruit body from the surrounding thallus. In Collema micro- 
phyllum (Stahl, 14) the proper exciple originates in paraphysis-like 
filaments and forms a pseudo-parenchymatous layer which surrounds 
the hymenium in much the same way as I find it in C. pulposum. In 
the latter species as growth continues and the apothecium enlarges, the 
whole structure is carried upward and with it some of the surrounding 
thallus, so that when the apothecia are old they may be somewhat above 
the surface of the thallus. A part of the thallus which has been carried 
upward and which surrounds the fruit body forms the thalloid exciple. 
Discussion. 
The Number and Structure of Carpogones. 
I have found the carpogones of Collema pulposum isolated or in 
groups of three or four. In the Collemas, Stahl found that the apothecia 
commonly arise each from a single carpogone. He also figured the carpo- 
gones of C. pulposum as isolated. This he found is typical for the genus. 
I have found thern only occasionally isolated. In Physma compactum 
(Stahl, 74), the fruit body is compound. Stahl observed also that 
the size of the mature apothecium is not correlated with the number of 
carpogones, since in Physma the apothecia are comparatively small. 
I have found considerable Variation in the size of the apothecia in my 
material, but have no evidence as to whether the larger size is the result 
of age or of the coöperation of several carpogones. An apothecium forms 
asci for more than one year, but for how much longer my data do not 
enable me to determine. In Lecanora suhfusca L., Baur (5) and Lindau 
(60) found the carpogones in groups of five to ten ; in Endocarpon minia- 
tum L., Baur found three to eight. Among ascomycetes other than 
lichens which have compound fruit bodies may be mentionecl Boudiera 
(Claussen, 18), Pyronema (Tulasne, Harper, Claussen) and Tlieco- 
iheus (Overton, 72). 
In my material, the filament which is to bear one or more carpo- 
gones, is very often at least, differentiated from the other hyphae by 
having shorter, broader cells. From this filament the coiled carpogones 
arise. These may, however, also branch directly from a vegetative liypha 
which is in no way differentiated. In the latter case the carpogones 
are more apt to be isolated. Stahl savs the carpogones arise from un- 
Archiv f. Zellforschung. X. 27 
