314 VEGETABLE ORGANOGRAPHY. 



in these plants differs much from ordinary ones, and 

 that those organs are only expansions of the stem, and 

 entirely of the same nature. 



Section III. 

 Of the HepaticcB. 



The structure of the Hepaticse is very similar to that 

 of Mosses, as regards the organs of nutrition ; but it pre- 

 sents some peculiarities which deserve to be mentioned 

 here with more care, since they tend to make us under- 

 stand the general organization of cellular plants. Let 

 us first commence with those Hepatic^ which most 

 resemble Mosses, in order to arrive at those which 

 approach the Lichens; for this family, although very 

 natural and not numerous, is a true group of transition. 



The Jungermannias, or at least the greatest number 

 of this genus, present such analogies to the Mosses, that 

 old botanists joined them together. They present, in 

 the same manner, a cylindrical stem, simple or branched ; 

 roots, primary and secondary ones, sometimes springing 

 from the leaves, and most frequently along the stem ; 

 and, lastly, sessile leaves, sheathing at the base, per- 

 sistent, scattered or distichous along the stem : all 

 these organs are, as in Mosses, composed of cellular 

 tissue, without any appearance either of stomata, tracheee, 

 or vessels. But the differences which may be observed 

 between the Jungermanniee and true Mosses are — 1st. 

 That the leaves of the former are constantly devoid of 

 nerves, and entirely composed of round cellular tissue. 

 2d. That they are more seldom entire, often dentated, 

 and differently divided or cut, especially at their apex, 



