IIEPATrCAK. 



153 



is not so in Aii/hoceros ; there the inner cells form a colninn of sterile tissue, the 

 columella (Fig. loi, D col), and the archesporium is cut otT from the outer cells by 

 further periclinal divisions, and is thus a layer of cells in the form of a bell 

 with the mouth downwards, a form which recurs among the Mosses in the 

 Sphagnaceae and Andreaeaceae. In Fig. loi D the layer outside the arche- 

 sporium, the wall-layer, has divided again. Further growth consists only in the 

 further development of the tissues thus formed. The sporogonia of Anthoceros 

 have besides an intercalary growth at their base which continues for a long 

 time. The upper part of the capsule may have opened for some time and discharged 

 its spores, while no spore-mother-cells even have been formed in the lower part ; the 

 capsule of A. giganteus reaches a length of seven centimetres. The genus Notothylas, 

 one of the Anthoceroteae, has capsules with a columella, and other capsules in which 

 the columella is much less distinct or not formed at all ; in the latter case the sterile 

 cells form a chambered tissue which fills the inside of the capsule, and the spore- 

 mother-cells lie in its cavities. By the formation of capsules without columellas 

 Noiothylas is connected with the rest of the Hepaticae, where also there are forms 

 in which the sterile cells of the capsules are not developed into elaters, but act as cells 

 of nutrition expending the food-material stored up in them in promoting the develop- 

 ment of the spores \ Smaller deviations in the formation of the embryo, especially 

 such as are caused by unequal development of separate parts, must remain unnoticed 

 in this place ". 



The Hepaticae may be divided into two series with intermediate forms in 

 either series : — 



1. Series of the Jungermannieae. 

 I {a) Jungermannieae. 



\ \l)) Anthoceroteae. 



2. Series of the Marchantiaceae. 



f {a) Riccieae. 



( \b) Marchantieae. 



Series of the Jungermannieae. 



(a) The Jungermannieae, alike from the number of their species and the frequency 

 of their occurrence, are much the largest group of the Hepaticae. It was stated above 

 that two subdivisions may be founded on the difference in the character of their 

 vegetative organs, namely the thalloid and the foliose; it was pointed out at the same 



^ The orientation of the cohimella oi Noiothylas differs from that oi Anthoceros, inasmuch as in 

 the latter the columella is a secondary product of differentiation inside the spore-chamber. 



2 If we take a survey of what has been said above, we shall see that, as Leitgeb has pointed out, 

 four types may be distinguished in the development and structure of the sporogonium. 



a. The sporogonium is differentiated into a layer of cells forming the wall and into an inner 

 space filled with spores only (Riccieae, in the narrower sense). 



l>. The cells of the inner space are divided into fertile cells which form spores, and sterile cells 

 which serve to feed the spores {Corsinia, Rielleae, Notothylas). 



c. The cells of the inner space which remain sterile become elaters most Hepaticae). 



(/. The axis of the capsule is traversed by a cellular column, the columella, which is surrounded 

 and arched over by the spore-forming layer (Anthoceroteae, but for Notothylas vid. sup. under /'). 



