220 
as many as eighteen have been quarried from an area of but fifty 
square feet. The largest is about three and one-half feet in diame- 
ter. “Pwo species are represented in the transparency. They must 
have reached heights of at least thirty feet, their columnar trunks 
above the expanded butts being crowned with large tripinnate 
fronds at least six feet long, the pinnules being small and bilobed 
and of a type known as Sphenopteridium. Instead, however, of 
producing spores as do all ferns, these fern-like fronds bore to- 
ward their tips pollen- and seed-producing organs. 
These are clearly shown in the pendant frond just to the left of 
the trunk, and in the one above in which the modified tip is outlined 
against the background of sky. The pollen was produced in distal 
clusters of funnel- or saucer-shaped affairs. 
jean 
The nut-like seeds, about a quarter of an inch in diameter, were 
borne in pairs at the ends of forked branchlets. They were oval 
in form and were enclosed in an outer husk or cupule, which ap- 
pears to have been lobed in some specimens. 
The seeds of all of the recognized seed-ferns, some of which 
were very much larger than those of Hospermatopteris, have been 
rather fully investigated in some of the Carboniferous petrified 
forms, and show that they were much more complexly organized 
than are the seeds of our modern flowering plants, although they 
do show many features similar to those of the seeds of the Maiden- 
hair Tree (Ginkgo) and the Cycads. 
Irom our present knowle¢ 
ean 
ge it would seem that the seed-ferns 
far outnumbered the true ferns during the Paleozoic. Some un- 
doubtediy continued into Mesozoic times, but the lack of struc- 
tural material of these later suspects has thus far made it impos- 
sible to satisfactorily demonstrate their true nature. 
7. Paleozoic Gymnosperms 
The Gymnosperms comprise that ancient and extensive group 
of mostly arborescent plants which do not have their seeds enclosed. 
Their outstanding characteristic is the exposed ovules, discovered 
by Robert Brown in 1827, and exemplified in the cone of a pine or 
spruce, and the open-topped berry of a yew. Pollination, accom- 
plished through the agency of wind in the Gymnosperms, brings 
t 
— 
1e pollen in direct contact with the ovule. In the flowering plants 
