472 The American Naturalist. [June, 
The amentaceous inflorescence predominating in the group 
bears a decided likeness to the cones of the Pines and 
Cypresses. Obviously then, the Dicline were the trees best 
fitted to battle with the central stronghold of the Mesozoic 
coniferous forest, and probably they were first fully developed 
on the inner portion of the tension-line, face to face with the 
strongest of the Conifers. Behind them, toward the outer edge 
stood the Tree-Ferns, Cycads, and Palms; but which, we may 
ask, were the Conifers that stood closest round about, among 
and before them? Probably the sub-order Taxinez, the frater- 
nity of broad-leaved Taxites and Gingkos. The power of this 
most ancient group of Conifers had, as we have seen, waned, 
and they must have been driven toward the outskirts of the 
forest by the stronger Cupressinez and Abietineæ. Here they 
must have met the early Diclinæ. Where did the Dicline 
develop the broad flattened leaf-blades that so strikingly distin- 
tinguish their foliage from that of our living Coniferee? Where, 
if not in a competitive struggle with the broad-leaved Taxinee 
of the Mesozoic forest-margin? he ancient Taxinez had re- 
produced in their foliage something of the character of the fern- 
fronds; the newer Pinaceæ had rather imitated and exagger- 
ated the scale-leaves of the great Carboniferous Lycopods. And 
finally, the broad leaves of the Taxines were perpetuated, 
under greatly improved and elaborated forms, in the Dicline. 
Through the Cretaceous the Coniferse rose to the zenith of their 
power; the Tree-Ferns and Cycads weakened ; the Palmace® » 
and Diclinæ, more particular] y the latter, fast gath ered strength 
toward the dominion they claimed in the succeeding Tertiary- 
Meantime, in the undergrowth and on the open margins of the 
forests, and on the open country that did not support a growth 
of trees, the evolution of the higher types of Monocotyls and 
Dicotyls was rapidly progressing. Many of the stronger forms 
became shrubs, and here and there a peculiarly favored type 
rose from lowly herbaceous to arborescent habit, and thus 
founded a new tree-group. Such, for instance, were the ‘al 
nolias and Tulip-Trees and Maples and many others. In : 
this we read an increasing complexity in the conditions pre 
sented to onward struggling plant-life, and here a vitally 1 - 
portant point rises for our consideration. 
(To be continued.) 
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