148 



SECOND GROUP. — MUSCINEAE. 



in many of the foliose Jungermannieae, Madotheca for instance, simple cells become 

 detached as gemmae in numbers from the margins of the leaves; in Blasia, Mar- 

 chantia and Lunularia special receptacles are formed on the upper side of the flat 

 shoots which is turned towards the light ; these receptacles are flask-shaped in Blasia, 

 broadly cup-shaped in Marchantia, half-moon-shaped with the enclosing projection 

 on the posterior side only in LuJiularia. Papillae arise on the bottom of these 

 receptacles, and their terminal cell developes into a flat body of some size, which 

 constitutes the gemma ; between them are club-shaped hairs, the cell-walls of which 

 swell into mucilage, and this ultimately forces the gemmae out of the receptacles. 

 There are indentations right and left on the margin of the lenticular gemmae of 

 Marchantia and Lunularia (Fig. 98, VI\ from which the first flat shoots appear, when 

 the gemmae have fallen out of the receptacle and are exposed on damp ground to 

 the influence of light. 



Fu,. 97. Marchantm folyinoypha, sligluly en- 

 larged. A. B young shoots. C the two shoots from a 

 gemma with receptacles ; v, -v the apical region in a 

 depression in the margin of the thallus. D a piece of 

 the epidermis seen from above; sp stomata on the 

 rhomboid plates more highly magnified. 



The sexual organs are formed in the thalloid Hepalicae on the upper side, the 

 side exposed to the light, and are usually sunk in the tissue of the thallus; in An- 

 ihoceros the antheridia are in close cavities. The sexual organs are either on ordinary 

 shoots or on specially modified branches, in which further growth ceases after the 

 organs are produced. This sexual shoot is developed in a peculiarly remarkable 

 manner in many Marchantieae. In M. polymorpha special shoots of singular 

 form rise erect into the air (orthotropous shoots) from the prostrate stem, bearing the 

 antheridia on the upper side, and the archegonia on the under side (though placed 

 originally on the upper side), and these shoots are distributed monoeciously or 

 dioeciously. We find such shoots in simpler form in thalloid Jungermannieae, 

 as in Aneura, where certain shoots are retarded in their growth and so come to 

 be lateral or to be placed on the ventral side of the branch- system, and these 

 produce antheridia or archegonia. In Metzgeria the sexual shoots spring from 

 the midrib and grow in so concave a form for the protection of the sexual organs 

 on their dorsal face, that they have the appearance of a leaf-like envelope. IMost 



