66 LECTURE V. 



typical leaf-shoots of vascular plants down to the simplest beginnings of shoot-, 

 formation; where, finally, there still remains of the shoot-nature only the rising 

 above- the substratum, the production of the generative organs, and the capacity 

 for assimilation with the irritabilities necessary thereto. 



We shall here refer only to some important points and give a few examples, 

 since these matters have been already spoken of. 



In the true Mosses, and, in the subdivision of the Liverworts, in the foliose 

 Jungermanniae, we find quite typical shoots, differentiated into leaves and axes, 

 but anatomically much simpler than those of the vascular plants. We have here 



. FIG. 6i. — Portion of transverse section of root of Cissus, c cambium ; h wood ; g large vessels. 

 The tissue bb belongs to the vegetative body oi Brugtnansia Zippelii, parasitic in the Ctssits root: its 

 thin fibres creep in the cortex of the Cissus root, and swell up here and there into thick cushions (as in 

 the tigure), from which flowers are developed, which then appear externally as in Fig. 17 A (strongly 

 magnified ; after Solms-Laubach). 



always to do with small plantlets, usually growing together in dense swards, 

 which only vegetate in moist air, and make use of a dried-up condition as a 

 period of rest. Accordingly, the necessity for the formation of wood and the con- 

 duction of water, and the arrangement of those anatomical points which bring about 

 the solidity of large land plants — all those arrangements generally which are only 

 necessary to large land plants — are wanting. In particular, the foliage leaves of 

 the Mosses, considering their small size and the life-conditions mentioned, do 

 not need to form a network of ribs and veins, as we found to be the case 

 with the large leaves of land plants: or, to express the causal relations more 



