Hypnum Nuttallii is distinguished from Hypnum aureum by its longer and more erect cylindrical capsule, shorter rostrate operculum, less perfect inner peristome, and especially by its much shorter pedicel and the strongly dentate lower margin of the leaf.
The same characters, together with its densely pinnate ramification, separate it from Hypnum lutescens.
These three species form a very natural group, composing the genus Camptothecium of the admirable Bryologia Europæa, and are remarkable for the presence of small male buds produced from spores, usually in clusters, and evidently parasitic on the fertile plants. The normal inflorescence, however, is said by authors to be dioicous.
TAB. 128.—Hypnum Nuttallh.
1. Planta fertilis naturali magnitudine.
2. Pars ramuli.
3. Folia ejusdem.
4. Areolatio folii baseos.
5. Eadem apicis.
6. Cellulæ ejusdem.
7. Sectiones transversalos folli.
8. Perichæthim.
9. Folium ejusdem.
10. Capsular operculatæ.
11. Particula peristomii.
12. Operculum.
13. Calyptra.
11. Pars pedicelli.
15. Inflorescentia pseudo-monoica.
16. Pars ramuli cum gemmis masculis parasiticis.
17. Folium perigoniale cum antheridio.
