1884. 47 : Trans AINA Vi JAG.Sct. 
striking exceptions in the broad leaves of Gingko and Phyllocladus. 
On the other hand Lfhedra, like many other desert plants, is almost 
without leaves. In the ferns and umbelliferee also we find the foliage 
very much dissected, almost as much so as that of aquatic plants— 
why, no one has yet given us a reason. 
It has been suggested that the earlier forms of leaves were simple, 
and that they have become compound by variation in descent. The an- 
cient history of plants, which I have studied with much interest, gives 
no support to such atheory. The groups of terrestrial plants which 
earliest assumed importance were the conifers and the lycopods, but 
they have retained practically the same forms of foliage from the 
earliest times to the present; the living Lycopodium dendroideum be- 
ing almost an exact copy in miniature of the Lepidodendra of the Coal 
Measures, while the Mesozoic and Paleozoic conifers exhibit the same 
scaled or acicular leaves that characterize the most abundant conifers 
of the present day. The Gingkos of the Mesozoic age generally had 
more divided leaves than the Sa/ishburia of the Tertiary and present 
times ; but on looking over the entire field, it is impossible to detect 
any progressive tendency to simplicity or complexity in the foliage of 
the conifer. The cycads, of which the golden age was the Jurassic, 
have always been characterized by pinnate fronds with often narrow 
pinnules ; but their first development was in the Coal flora in the form 
of Cordaites and Noeggerathia, in which the leaves were broader than 
in most later species. 
The monocotyledonous plants, the grasses and palms, the yuccas 
and pandanus, have, as a general rule, narrow leaves and a parallel 
nervation, for which no adequate explanation has been offered ; while 
some of the lilies and most of the arums have broad leaves of a 
totally different structure. ~ 
The broad-leaved angiosperms begin in the Cretaceous, and speedily 
acquire pre-eminence in the vegetation of the globe. We now have 
the life history of this group pretty well outlined in the elaborate 
figures and descriptions of the Cretaceous and Tertiary floras, but we 
look here in vain for any law of development in leaf-forms. Among 
the earliest plants are the magnolias, remarkable for the simplicity of 
their leaves, their entire margins, and their camptodrome nervation. 
With these are oaks, generally with toothed, but only later cut and 
lobed leaves; willows, with simple leaves like those of the present 
day ; Liguidamébar, with species in the Cretaceous and Tertiary, hav- 
ing leaves with broader lobes than the living one, and yet not decidedly 
different ; Aralias, with digitate leaves, and Platanus and Sassafras, 
with broadly lobed leaves, were conspicuous elements in the earlier 
angiosperm flora, but they were essentially what their representatives 
