1897] PHYLOGENY AND TAXONOMY OF THE ANGIOSPERMS 147 
_ the present classes of the pteridophytes,—the ferns, joint-rushes, 
and lycopods. There appears to be no doubt that heterospory 
was attained by some of the Devonian pteridophytes. The 
Lepidodendree were quite certainly heterosporous, and possibly 
the Psilophytee should be admitted also. Certain it is that the 
conifers of this period were heterosporous. 
In the Carboniferous and Permian the species and genera of 
then existing types were multiplied, and the cycads, another 
heterosporous type, were added. This tendency to heterospory 
soon resulted in the appearance of plants referred by some 
authors to the monocotyledons. It is pretty certain at any rate 
that monocotyledons appeared late in the Paleozoic period or 
early in the Mesozoic. Of dicotyledons no fossils have been 
determined with certainty earlier than the Cretaceous, in which 
period they were evidently quite abundant. ‘ 
If now we examine with some detail the fossil remains of the 
angiosperms we find that the earliest recognized were mono- 
cotyledons with superior ovaries (Paleospatha, Spirangium, 
Yuccites, from the Permocarboniferous and the early Mesozoic). 
Making due allowance for possible errors of determination we 
find that by the end of the Jurassic period the monocotyledons 
were probably represented by members of the groups (orders) 
Apocarpz, Coronariez, Calycinz, and Glumacee. To these we 
may add, in the Cretaceous, a few representatives of the Epi- 
Synz. In the Tertiary the plants determined are referred to 
the Apocarpe, Coronarieze, Nudiflore, Calycine, Glumacee, 
Hydrales, and Epigyne. It is interesting to note that the 
monocotyledonous plants of the Tertiary have been referred 
Mainly to the hypogynous orders, and that none have been 
identified as representing the Microsperme. Apparently the 
evolution of the monocotyledons began with hypogynous 
species and proceeded toward those in which epigyny is most 
marked. Orchids are doubtless of very late evolution, so late 
_in fact that none have been preserved as fossils. 
The foregoing facts are presented below in tabular form, the 
per cent. of representation of each group being given for each 
