Page:History of botany (Sachs; Garnsey).djvu/221

fertilisation of these organs proceeds the root-bearing and leafy stem of the Fern, which in its turn again produces only asexual spores. In the Muscineae, on the other hand, a much differentiated and usually long-lived plant is developed from the spore, and this plant proceeds again after some time to form sexual organs, the product of which is the so-called Moss-plant. The first generation that arose from the spore, the sexual, is in the Muscineae the vegetative plant, while in the Ferns and their allies the whole fulness of vital activity and of morphological differentiation is unfolded in the second generation which is asexually produced. Here all was at once clear and obvious; but Hofmeister's researches also showed that the same scheme of development holds good in the Rhizocarps and Selaginellae where two kinds of spores are formed; and it appeared plainly from their case that the recognition of the true relation between the production of spores and sexual organs is the guide to the morphological interpretation. When the processes in the large female spore of the most perfect of the Cryptogams was known, the formation of the seeds in the Conifers was at once understood; the embryo-sac in these answered to this large spore, while the endosperm represented the prothallium, and the pollengrain the microspore; the last trace of alternation of generations, so obvious in the Ferns and Mosses, was seen in the formation of the seed in the Phanerogams. The changes, which the alternation of generations passes through from the Muscineae upwards to the Phanerogams, were, if possible, still more surprising than the alternation of generations itself. The reader of Hofmeister's 'Vergleichende Untersuchungen' was presented with a picture of genetic affinity between Cryptogams and Phanerogams, which could not be reconciled with the then reigning belief in the constancy of species. He was invited to recognise a connection of development which made the most different things appear to be closely united together, the simplest Moss with Palms, Conifers, and angiospermous trees, and which was incompatible with the