i6o MUSCINE.'E 



in the Ricciaccc^ and Marchantiaceae it bursts irregularly, and the wall 

 is composed of a single layer of cells without ornaments, or nearly so. 

 The spores also vary considerably in the different orders. In many 

 Jungermanniaceas the spore has only a single cuticularised membrane, 

 which is entirely used up in the formation of the germinating filament. 

 In most genera the wall is composed of two distinct separable layers, 

 the exospore and endospore ; while in Sphaerocarpus (Mich.), Corsinia 

 (Radd.), and some others there is a third outer layer, often beautifully 

 sculptured, which is derived from the membrane of the special mother- 

 cells of the spores. This layer is called by Leitgeb the periniiau. 

 AVarnstorf (Verhandl. Bot. Ver. Brandenburg, 1886, p. 181) finds in 

 Blyttia (Endl.) two kinds of spore, larger and smaller, which he believes 

 to produce female and male plants respectively. In Sphaerocarpus the 

 spores are combined into tetrads. When the spore germinates, the 

 endospore breaks through both exospore and perinium, when the latter 

 is present, and protrudes as the first rhizoid. 



Literature. 



Bischofif— Nov. Act. Acad. Leop. Car., 1835. 



Gottsche— /(^/^., 1838. 



Gottsche, Lindenberg u. Esenbeck — Synopsis Ilepaticarum, 1844. 



Kny — Pringsheim's Jahrb. wiss. Bot., 1865, p. 64. 



Leitgeb — Bot. Zeit., i87i,p. 557, and 1872, p. 33 ; r^Iittheil. naturw. Ver. Steiermark, 



1872 ; Unters. liber die Lebermoose, 1874-1881; and Ber. Deutsch, Bot. Gesell., 



1883, p. 246. 

 Janczewski — (Archegone) Bot. Zeit., 1872, p. 372 et seq. 

 Carrington— British Hepaticae, 1874. 

 Kenitz-Gerloff — Bot. Zeit., 1875, pp. 777 et seq. 

 Vochting — Pringsheim's Jahrb. wiss. Bot., 1885, p. 367. 

 Satter — Sitzber. Akad. Wiss. Wien, 1882. 

 Leclerc du Sablon — (Antherozoids) Comptes rendus, cvi., 18S8, p. '^'](>. 



Liverworts are distributed throughout the entire globe, growing 

 mostly in moist situations. Many tropical species are epiphytic on the 

 leaves of Flowering Plants or ferns. They are of no economic importance. 

 They are classified under five orders, of which the first includes both 

 foliose and thalloid, the remaining four almost entirely thalloid, forms. 



Order i. — Juxgermanxiace.e. 



In this, much the largest order of the class, are included genera with 

 every variety of vegetative development, from an undifferentiated thallus 

 to a slender filiform stem, with sessile leaves seated either in two rows on 

 the upper side, or in three rows, two of them on the upper, and the third, 

 the a?nphigasters, smaller and adpressed to the under side. The thalloid 



