The Andreaacete are entirely confined to granite or slate rocks and 

 boulders, and to mountains, stony regions, or the high latitudes of the arctic 

 and antarctic zones, and this no doubt accounts for the great uniformity in 

 their structure and habit. The pachydermous nature of their cells gives the 

 leaves an almost cartilaginous texture, and thus enables them to resist the 

 pelting storms which harass the elevated districts they inhabit, and produce 

 that debris of their tissues and of the adjacent rocks, which always more or 

 less infiltrates the tufts. This thickened cell tissue, combined with the dark 

 color, greatly obscures the definition of the nerve and cells under the 

 microscope, and a preparatory treatment with Liq. Soda? or Potassae will be 

 found of the greatest assistance in their examination ; by placing a moistened 

 branch in a few drops of the caustic alkali on a slide, heating it over a 

 spirit lamp, and then soaking well in clean water, the leaves become soft 

 and flaccid, and every cell clearly defined. 



The family includes but a single genus of about 50 species, which may 

 be arranged in three sections. 



1. Euandreaea. LINDB. Marked by its distinct convolute perichaetium, 

 and deeply 4-fid capsule. 



2. Chasmocalyx. LINDB. Without any evident perichaetium, and deeply 

 4-8 valved capsule ; includes only A . nivalis HOOK, and australis 

 F. MUELL. 



3. Acroschisma. HOOK. WILS. Having the capsule cleft only at the 

 upper end into 4-8 valves; comprising A. Wilsoni HOOK, and densi- 

 folia MITT. 



The greatest number of species is found in the islands of the antarctic 

 regions, but a fair proportion is also met with on the elevated mountains of 

 South America, while Northern India and Australia also possess certain 

 endemic forms ; in Europe the Scandinavian peninsula is the head-quarters 

 of the family. 



Several minute branched lichens Ephebe pubescens, Leptogium muscicola, &c., 

 occasionally infest the leaves, but in the S. American A . arachnoidea C. Mull ; 

 the leaves are overrun with minute filaments, truly produced by the plant 

 itself. For an exhaustive account of the development and structure of these 

 plants, we may refer to the admirable paper of Kiihn " Entwickelungsgeschichte 

 der Andreaaceen" (Leipzic, 1870), and an equally valuable one by Berggren 

 " Studierofver Mossornas byggnadochutveckling" in Act. univ. Lund. IV. n. 12 

 (1867) ; both of which are illustrated by excellent plates. 



ANDRE^A. EHKHART. 



Hannov. Mag. 1778, 101 Stuck, p. 1601 ; et Beitr. i. pp. 15 e t 180 (1787). 



Acrocarpous mosses of a reddish, brown or black color, growing in 

 small dense fragile tufts. Capsule sessile on the elongated vaginula, 

 splitting into 4 rarely 6 or 8 valves, united at base and apex. 

 Calyptra thin, adherent, mitriform, torn irregularly. 



Dillenius was the first author who recognized any species of the present 

 genus, and he described and figured two in his Historia Muscorum, under 

 the names Ltchenastrum alpinum atrorubens tens, calycibus squamosis " (A. alpina), 



