1 74 MORPHOLOGY. 



reticulated thickening layers. The pedicle of the sporocarp con- 

 sists always, up to the period of maturity, of a delicate cellular 

 tissue, which expands with wonderful rapidity, but at the same 

 time also decays very quickly. The wall of the capsule consists, 

 with few exceptions, of an epidermal layer (of flat and mostly 

 brown-coloured cells), and of an inner layer of spiral-fibrous cells. 



Liverworts deserve, in an anatomical point of view, much more 

 thorough and comprehensive investigations than they have as yet met with. 

 We most certainly possess the complete monography of Mar chantia poly - 

 morpha furnished us by Mirbel, who has also given us plates which do 

 more to dazzle by the brilliancy of their colouring than to satisfy, on all 

 points, with respect to their fidelity to nature : but Mirbel leaves many ques- 

 tions unanswered, and his statements have already met with many correc- 

 tions. Here, as everywhere else, we look in vain for an exact and complete 

 history of the course of development. The formation of the spiral fila- 

 ments in the elaters and the walls of the fruit have been observed by 

 Meyen. According to his views, they arise from the perceptible con- 

 fluence of the globules of chlorophyll into a spiral band. Gottsche posi- 

 tively denies this to be the case, and, as far as I have been able to con- 

 vince myself in Pellia epiphylla, I think he is in the right. They differ 

 in their fully developed condition from all other spiral filaments by their 

 deep brownish yellow colour, which reminds us of the cells of the sheaths 

 of the vascular bundles in the Ferns. A few special peculiarities present 

 themselves in Liverworts ; thus in the Marchantice we find air-cavities, 

 in Pellia epiphylla a singular system of intercellular passages, which 

 convey, not air, but a yellowish and, in the case of Var. ceruginosa, a 

 reddish juice.* Still more remarkable is the system of tubes discovered 

 by Gottsche in Preissia commutata, running through the cells, and 

 apparently perforating their walls : the only analogy with this case pre- 

 sents itself in the tubular convolutions of the root-cells of Neottidium 

 nidus avis (vol. i. . 39). 



V. MOSSES (Muscr FRONDOSI). 



100. The spore-cell expands, emerges from its torn outer coat, 

 and, new cells being developed at the free end, forms for itself 

 a filamentous tissue, composed of linear cylindrical cells ranged 

 end to end (the proembryo). At one point, the filaments of this 

 tissue become contracted into a node composed of closely com- 

 pressed roundish cells ; this node, elongating itself upwards, becomes 

 the stem, on which leaves are simultaneously formed. More rarely 

 the plant remains simple (as in the annual Phascum, and in the 

 perennial Polytrichum), but there generally appear at the axils of 

 the leaves small buds, by which means the stem ramifies. The 

 form of the uniformly simple flattened leaves (which are never 

 lobed) varies between almost circular, linear-lanceolate, and linear; 

 they sometimes exhibit two streaks of denser, more compressed, 



* Compare Wiegmann's Archiv, Jahrg, v. vol. i. p. 280. (1839). 



