res which belong to the
Angiosperms, the Gymnosperms and the Ferns.

ii. ORIGIN OF SEED-PLANTS.

The general relation of the gymnospermous Seed-plants to the Higher
Cryptogamia was cleared up, independently of fossil evidence, by the
brilliant researches of Hofmeister, dating from the middle of the
past century. (W. Hofmeister, "On the Germination, Development and
Fructification of the Higher Cryptogamia", Ray Society, London, 1862.
The original German treatise appeared in 1851.) He showed that "the
embryo-sac of the Coniferae may be looked upon as a spore remaining
enclosed in its sporangium; the prothallium which it forms does not come
to the light." (Ibid. page 438.) He thus determined the homologies on
the female side. Recognising, as some previous observers had already
done, that the microspores of those Cryptogams in which two kinds of
spore are developed, are equivalent to the pollen-grains of the higher
plants, he further pointed out that fertilisation "in the Rhizocarpeae
and Selaginellae takes place by free spermatozoa, and in the Coniferae
by a pollen-tube, in the interior of which spermatozoa are probably
formed"--a remarkable instance of prescience, for though spermatozoids
have not been found in the Conifers proper, they were demonstrated
in the allied groups Cycadaceae and Ginkgo, in 1896, by the Japanese
botanists Ikeno and Hirase. A new link was thus established between the
Gymnosperms and the Cryptogams.

It remained uncertain, however, from which line of Cryptogams the
gymnospermous Seed-plants had sprung. The great point of morphological
comparison was the presence of two kinds of spore, and this was known to
occur in the recent Lycopods and Water-ferns (Rhizocarpeae) and was
also found in fossil representatives of the third phylum, that of the
Horsetails. As a matter of fact all the three great Cryptogamic classes
have found champions to maintain their claim to the ancestry of the
Seed-plants, and in every case fossil evidence was called in. For a long
time the Lycopods were the favourites, while the Ferns found the least
support. The writer remembers, however, in the year 1881, hearing the
late Prof. Sachs maintain, in a lecture to his class, that the descent
of the Cycads could be traced, not merely from Ferns, but from a
definite family of Ferns, the Marattiaceae, a view which, though in a
somewhat crude form, anticipated more modern ideas.

Williamson appears to have been the first to recogn