DICRANACEAE 21 



GROUP I. APLOLEPIDEAE 



Peristome single, composed of two layers of plates made by 

 a deposit on the inner and outer side of the original cell-wall. 

 In the outer layer a single undivided plate forms the entire 

 width of the tooth, but the inner plate is divided by a median 

 line into two parts. The teeth are often partially split along 

 this median line as in Dicranum , or entirely cleft to the base as 

 in Barbula. Ceratodon represents an intermediate condition. 

 With the exception of some species of Fissidens, our Aplolepideae 

 are acrocarpous. 



Family 6. ARCHIDIACEAE 



Small terrestrial mosses, mostly perennial; 0.5-1.5 cm. high; 

 branching by innovations below apex. Central strand present. 

 Leaves lanceolate, costate. Capsule apparently sessile, spher- 

 ical, cleistocarpous, of a single layer of cells, producing about 16 

 very large polyhedral spores, the largest known in the mosses. 



Except for the peculiarities of the capsule wall and spores 

 this family is close to the cleistocarpous Dicranaceae. The 

 capsules often appear lateral, either by successive innovations 

 or by developing on a short branch. The only genus is 



ARCHIDIUM Brid. 



A. Ohioense Schimp. "Flat rocks, Palisades, Bergen Co., 

 N. J.," Austin, Bx! Autumn to spring. 



A. alternifolium (Dicks.) Schimp. "Old fields near N. Y. 

 City," Austin, Bx! (As Phascum alternifolium.) 



A. alternifolium is paroicous with leaf cells up to 27 by 135^, 

 while A. Ohioense is autoicous, leaf cells 13 by 54^. 



Family 7. DICRANACEAE 



Plants varying in size from exceedingly minute to several 

 inches in height, dichotomously branched. Leaves broadly 

 lanceolate to subulate, often sheathing at base, costate, occa- 

 sionally papillose; leaf cells quadrate or rectangular to linear, 

 chlorophyllose above, more elongated and with little or no 



