428 pees tructural and Physiological Botany. 
The uniformity of vegetation characteristic of the Carbo- 
niferous is still more marked in the Triassic system. | 
Next in succession above the Trias is the /urassic sys-. 
tem, which again is divided into three sections, the Zzas, and 
the Lower and Upper Oolite. The fossil remains found in this 
formation lead to the conclusion that the marine plants of. 
the Lias did not differ essentially from those of the present | 
time in their external appearance, although the species may 
have been very dissimilar. ‘The case is different with the 
terrestrial vegetation, in which we still find a considerable 
coincidence with that of the Keuper. The prevalent forms 
in the forests consisted of Cycadez, of which fifty-eight 
species have been described. From this point, this beau-. 
tiful form of vegetation, which in regard both to its habit, 
and to its morphological and anatomical structure occupies 
an intermediate position between the Ferns, Palms, and Coni- 
ferze, decreases, only a few species existing at the present 
time. With these were associated numerous Coniferz nearly 
related in form to our Araucariasand Thujas. ‘The under- 
wood of the forest still consisted of Ferns, along with fleshy 
Fungi. The marsh-loving Calamites have disappeared, and 
the Equisetacee of that period scarcely exceeded our own 
in size. Plants allied to Typhaceze, Naiadesze, Cyperaceee, and 
Juncacee, fringed the edges of the water. This sketch gives, 
however, only an imperfect idea of the vegetation of that 
system ; for its coal shows that in magnitude it must have 
resembled that of the Carboniferous period. The vegetation 
of the Lower Oolite presents no great difference from this, — 
A number of sea-weeds have been preserved ; the earlier 
forms of Ferns and Cycadeze disappear, and others take their 
place more nearly related to those of the present time. The 
flora of the Upper Oolite does not include any marine plants, — 
only a single freshwater Alga, and in other families also 
fewer forms than the Middle period. ‘There would seern to 
have been an exhaustion of the earth similar to that which 
apparently succeeded the Carboniferous period. . 
