O. soRDiDUM S & L. Plate VI. Somewhat resembles the preceding in 

 leaf characters, but the leaves, though acute, are broader pointed with 

 thinner cell walls. It is at once distinguished by the immersed or emergent 

 plicate capsules and smooth segments. The spores mature in late spring 

 or summer. 



This species is so close to the var. fastigiatiwi of O, ajffine that it may- 

 cause confusion, especially as the the teeth of sordiduin are often as mark- 

 edly trabeculate at the summit as those of fastigiatum figured by Limpricht 

 (Laubmoose 2:82), but both affi.7ie and its var. are rare. I have not been 

 able clearly to differentiate sordidum from affine, and incline to the 

 opinion that they are forms of the same species for all except the experts. 

 All our ordinary forms are sordidum^ however. O. afflne. is certainly treated 

 differently by European authors and is exceedingly variable. The capsule 

 of sordidum is often so strongly contracted under the mouth as to resemble 

 strangulattim except for the larger size of the plant and the lighter color of 

 the capsule. 



O. striatum (L.) Hedw. {O. leiocarptim B. & S.) isa rare species, with 

 capsule almost as smooth as in O. speciosum, and it has been confused with it 

 by several good bryologists, but the capsules are immersed or only slightly 

 emergent and ovoid; teeth i6, separate, and i6 comparatively broad seg- 

 ments. 



In August I have found O. speciosuDi, O. sordidum, O. strangulatum, 

 and (9. Ohioense growing together on fruit trees. O. strangzi latum is much the 

 the most abundant, and is easily recognized by the strangulate, dark red- 

 brown capsules appearing as described in the text. O. Ohioense is about the 

 same size, but the straw-colored capsules catch the eye at once. O. sordidum 

 stands out at once by reason of its greater size and larger leaves and cap- 

 sules less plicate than in O. strangulattim. O. speciosum is somewhat smaller 

 than sordidum, and at this time the capsules are immature with the hairy 

 calyptra still firmly attached. The comparative sizes of speciosum and 

 sordidum is just the reverse of what my herbarium specimens and the book 

 descriptions lead me to expect, as the specimens of speciosum I collected were 

 much smaller than those in my collection. 



I desire to acknowledge my indebtedness to Dr. G. N. Best for notes and specimens, 

 and to Mrs. Britton's published notes on this genus. 



This monograph is taken from the MS. of a new moss book now in preparation by 

 the writer. I should be very glad to receive criticisms from any one who may have occa- 

 sion to use it, to the end that I may succeed in making as helpful a book as possible. 



A. J. G, 



Description of Plate VI. 



Fig. r — Plants natural size. Fig. 3 — Leaves. Fig. 4 — Leaf sections. 

 Fig. 5— Cellular structure of leaf base and apex. Fig. 12 — Antheridial branch 

 with antheridium and paraphysis. Fig. 11— Segment of peristome highly 

 magnified. Fig. 13 — Superficial stoma. The other figures are self explan- 

 atory. 



