XXvill EXPLANATION OF THE PLATES. 



PLATE XXI. 



1. Ptychomitrium polyphyllum. 



a. plant, nat. size. 



b. leaf, magnified. 



c. sporangium, magnified. 



d. portion of peristome, magnified. 



2. Glyphomitrium Daviesii. 



a. plant, nat. size. 



b. leaf, magnified. 



c. veil, magnified (generally plicate). 



d. sporangium, magnified. 



e. portion of peristome, magnified. 



3. Kacomitrium aciculare. 



a. plant, nat. size. 



b. leaves, magnified. 



c. sporangium, magnified. 



d. portion of peristome, magnified. 



e. tip of tooth, more highly magnified. 



4. E. heterostichum. 



a. plant, nat. size. 



b. leaf, magnified. 



c. sporangium, magnified. 



d. portion of peristome, magnified. 



5. Grimmia pulvinata. 



a. plant, nat. size. 



b. leaf, magnified. 



c. sporangium, magnified. 



d. portion of peristome, with ring, magnified. 



6. Schistidium apocarpum. 



a. plant, nat. size. 



b. leaves, magnified. 



c. sporangium, magnified. 



d. portion of peristome, magnified. 



e. columella, with lid attached, magnified. 



