CHAP.V.] the Influence of the Knowledge of Cryptogams. 201 



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 differ- 

 entiated 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 under- 

 stood ; the embryo-sac in these answered to this large spore, 

 while the endosperm represented the prothallium, and the pollen- 

 grain the microspore ; the last trace of alternation of genera- 

 tions, 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 Untersuchun- 

 gen ' was presented with a picture of genetic affinity between 

 Cryptogams and Phanerogams, which could not be recon- 

 ciled 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 



