The fathers of botany neglected everything else in order to concentrate their attention upon the flowering plants, from which very nearly all useful vegetable products were derived. The lack of adequate microscopes rendered it almost impossible to investigate the structure and life-history of ferns, mosses, fungi, and algæ until the nineteenth century. As late as the time of Linnæus it was possible to maintain that they developed spontaneously, though the great naturalist himself called them Cryptogamia, thereby expressing his conviction that they reproduce their kind like other plants, but in a way so far not understood. Gaertner, a contemporary of Linnæus, pointed out one important respect in which the spores of cryptogams differ from the seeds of flowering plants, viz. that they contain no embryo. _Ferns._—Even before the age of Linnæus it was known that little ferns spring up around the old ones, and that a fine dust can be shaken from the brown patches on the back of ripe fern-leaves. The dust was reputed to be the seed of the fern, and in an age which believed in magic the invisibility of fern-seed made it easy to suppose that the possessor of fern-seed would become invisible also. When the microscope began to be applied to minute natural objects, the brown patches of the fern-leaf were closely examined. William Cole of Bristol (1669), Malpighi, Grew, Swammerdam, Leeuwenhoek, and others, found the stalked capsules (sporangia), their elastic ring and the minute bodies (spores) lodged within them; it seemed obvious to call the capsules ovaries and the spores seeds. Some time in the latter part of the seventeenth century Robert Morison, professor of botany at Oxford, who died in 1683, sowed spores of the harts-tongue fern, and next year got an abundant crop of prothalli, which he took to be the cotyledons. A little later, when it had been proved that flowering plants possess male and female organs, diligent search was made for the stamens and pistils of ferns and mosses, which of course could not be found, though identifications, sometimes based upon a real analogy, were continually announced. Late in the eighteenth century one John Lindsay, a surgeon in Jamaica, who was blest with leisure and a good microscope, repeated the experiment of Morison, which seems to have been almost forgotten. Having remarked that after the rains young ferns sprang up in shady places where the earth had been disturbed. it occurred to him to mix the fine brown dust from the back of a fern-leaf with mould, sow the mixture in a flower-pot, and watch daily to see what might come up. About the twelfth day small green protrusions were observed, which enlarged, sent down roots, and formed bilobed scales, out of which young ferns ultimately grew. In 1789 Sir Joseph Banks, who was reputed to be the best English botanist of the day, asked Lindsay's help in sending West Indian ferns to Europe. Lindsay replied that it would be easier to send