44 American Midland Naturalist Monograph No. 6 



in old specimens finally break apart at the apex and coil over each other when 

 dry; spores .030-.040 mm, roughish, ripening in summer. 



On non-calcareous rocks. Greenland to Michigan and Georgia; and in 

 Northwestern United States. 



Fayette Co.: On rocks at White Rock, on Chestnut Ridge above Fairchance. Aug. 

 9, 1931. John L. Sheldon (figured). 



Order III. Bryales — True Mosses 



This order comprises numerous mosses of various habit: the endothecium 

 gives rise to the sporogenous tissue, which surrounds an inner sterile tissue, 

 loose in Arch.dmm, but forming the columella in the rest of the Bryales; the 

 spore-sac is separated from the wall of the capsule by a more or less highly 

 developed air-cavity; there is no pseudopodium but there is a more or less 

 elongated true seta; the outer wall of the archegonium after some growth is 

 ruptured, thus forming a basal vaginule and an apical calyptra; capsule cleisto- 

 carpous or, more usually, with a definite operculum and then often with a 

 single or double peristome: the order is conveniently divided, according to the 

 position of the sporogonium upon the leafy shoot of the gametophyte, into the 

 acrocarpous mosses (sporogonium at the apex of the leafy shoot) and pleuro- 

 carpous mosses (sporogonium lateral upon the leafy shoot) . 



ACROCARPI 



The acrocarpous mosses comprise about thirty families of the Bryales 

 widely distributed and numerous in number of species. For the analytical key 

 to the acrocarpous mosses see the general key to the genera of mosses at the 

 beginning of the book, page 10. 



Family 1. Archidiaceae 



Autoicous, sometimes paroicous or synoicous, rarely dioicous: small terres- 

 trial plants, closely gregarious and forming broad patches; stems erect, with 

 central strand, below bearing rhizoids; leaves of the shoots and also the basal 

 leaves minute, spreading, distant, linear-lanceolate, acuminate, flat, entire, the 

 costa ending in the point; perichastial leaves much larger, imbricated, more or 

 less linear-acuminate from a lanceolate base; leaf-cells smooth, prosenchymatous 

 or sometimes sub-vermicular to parenchymatous: capsule sessile, spherical, 

 terminal, non-operculate; columella none; spores commonly 16-20, about .2 mm 

 in diameter. 



One genus only, the characters being as given for the family, comprising 

 about 25 species, distributed widely in the temperate zones. Six species are 

 native in North America, but only one is likely to be collected in our region. 



1. Archidium Bridel 

 1. Archidium ohioense Schimper 

 Occurs on the ground in meadows and fields throughout eastern United 

 States from Quebec and Minnesota to Florida and Louisiana. Not yet re- 



