170 



MUSCINE^ 



in rows directed upwards, but not actually reaching the epidermal layer 

 of cells through which the stomates penetrate ; while beneath them is 

 the non-chlorophyllous layer, consisting of cells longest in the hori- 

 zontal direction without intercellular spaces. Each stomate has a number 



^__ of guard-cells formed by 



radial cell-divisions. The 

 details in the structure of 

 the stomates differ in the 

 different genera. Leitgeb 

 describes them as of two 

 kinds, simple and canali- 

 culate. The former are 

 epidermal pores situated 

 immediately above the air- 

 chambers ; the latter, which 

 occur in Marchantia and 

 Preissia, have the ap- 

 pearance of canals exca- 

 vated in the surface of the 

 thallus. Some of the rhi- 

 zoids of Marchantia are 

 characterised by singular 

 internal thickenings to the 

 cell-wall. The peculiar non- 

 sexual organs of propagation 

 of ^Marchantia, Lunularia 

 (Mich.), and other genera, 

 known as cupules^ have 

 already been described (figs. 

 150, 155). A peculiar non- 

 sexual mode of propagation 

 by means of gemmae occurs 

 in Fegatella (Radd.). 



The sexual reproductive 

 organs of the Marchanti- 

 aceae are, in most of the 

 genera, borne on erect 

 branches of the thallus of a peculiar umbrella-like form, which have been 

 variously termed receptacles^ discs ^ and inflorescences. They may be male, 

 female, or bisexual ; and, when unisexual, the species may be monoecious 

 or dioecious. In Fegatella the male inflorescences are oval discs sessile 

 upon the thallus (fig. 152). The inflorescence is generally regarded 



Fig. 158. — Development of archegone of M. polymorpha 

 (x 300). / — F", before, VI — VIII, afcer fertilisation, e, 

 central cell with oosphere ; f, young embrj-o ; si, lowest cell 

 of axile row ; pp, perigyne. IX, immature sporogone in 

 venter of archegone (x 30); a, neck of archegone ; st, 

 stalk of sporange which contains young spores and elaters. 

 (After Goebel.) 



