OF ARTS AND SCIENCES. 49 



accurate account, I do uot consider it necessary to occupy time and 

 space in describing the process in detail. The figure (Plate VIII. 

 Fig. 38) represents with sufficient accuracy the structure and general 

 appearance of the ascogoniuin and trichogyne. The same remarks ap- 

 l>\y to CoUe ma pulposum, (Bernli.) Nyl.,and Collema nigrescens, (lluds.) 

 Ach. The latter gives peculiarly good results, showing that the stages 

 of development from the formation of the ascogonium to that of the 

 mature spermogonium agree exactly with those described by Stahl in 

 C microphylluin, Ach. Sections made near the margin of the thal- 

 lus, which is generally beset with young apothecia, show large num- 

 bers of primordia consisting of a large-celled coil invested more or 

 less closely by branches of the neighboring hyphse, lying between the 

 young apothecia. (Plate VIII. Fig. 41.) Coils not yet thus invested 

 are more rarely seen. They do occur, however, and the following 

 points may readily be established. (Plate VIII. Fig. 40.) With iodine 

 they do not turn blue, but give a very pronounced protoplasmic re- 

 action. They arise directly from an ordinary thallus hypha, form 

 two or three spiral coils, and are then prolonged upwards in the form 

 of a straight or curved multicellular trichogyne. The tip rises above 

 the surface, swells considerably, and is cut off by a cross wall arising 

 at the base of the swollen portion. I was unable to see the act of fer- 

 tilization, or the subsequent changes in the trichogyne, but the later 

 development corresponds exactly with that of C. microphyllum. 



It is possible now to summarize our knowledge of the reproductive 

 process in the Collemaceaj as follows, bearing in mind that this list in- 

 cludes all the species thus far studied, and only those : — 



I. Type characterized by the transformation of the spermogonium 



into au apothecium after the fertilization of the carpogonium. 



Physma franconicum, Mass. ) /~i i, , , . , 



'' "^ ' i = (joUema cnaiazanum, Ach. 



" compactum, Mass. ) 



" myriococcum, Mass. = Collema myrioeocciim, Ach. 



*' Miilleri, Hepp, = Collema myriococcum, Ach. 



II. Type characterized by complete separation, throughout their 



course of development of spermogouia and apothecia. 

 Leptogium Hildenhrandii, Nyl. 

 " Menziesii, Nyl. 



saturninum, JNyl. v. _ Zieptogium myochroum, 



Mallotium tomentosum, Krb. (Ehrh. Schaer.) Tuck. 



Collema tomentosum, Hoffm. 



*' satiirninimi, (Dicks.) Ach. J 



VOL. XXV. (n. S. XVII.) 4 



