44 History of the Sexual Theory. [BOOK in.

covery to systematic botany has been already noticed. The conception of these relations developed by Hofmeister was not less important to the doctrine of the sexuality of plants ; it swept away at one stroke all the old false analogies between Phanerogams and Cryptogams and brought to light the real agreement ; Hofmeister had detected in the archegonium of the Cryptogams the body which is developed there, as in the ovule of the Phanerogams, into an embryo after fertilisation, namely the germinal vesicle or egg-cell. Here was the point of departure for all further systematic comparison in the sexual propagation of Cryptogams and Phanerogams. All beside was of secondary importance, even the fact, that the fertilisation of the egg-cell in the Cryptogams is not effected by a pollen- tube, but by spermatozoids. It was now easy to show the corresponding relations of generation in the other cases which Hofmeister had not yet observed.

Hofmeister's statements and conclusions respecting Sela- ginella and Isoetes were confirmed and some additions made to them by Mettenius in 1850, and in 1851 appeared Hof- meister's exhaustive work ' Vergleichende Untersuchungen, 1 in which the mode of production of the embryo in Coniferae was represented as an intermediate form between those of Phanerogams and Cryptogams. Further contributions were made to the knowledge of the subject ; Henfrey confirmed Hofmeister's results in the case of Ferns ; Hofmeister him- self and Milde observed in 1852 the history of fertilisation in Equisetaceae, and the former supplied at the same time a more complete account of the development of Isoetes; in 1855 he described the decisive points in Botrychium and Mettenius in 1856 those in Ophioglossum.

The processes of development before and after fertilisation were now cleared up by all these discoveries, but the direct observation of the act of fertilisation was still wanting. Hofmeister ('Flora,' 1857, p. 122) describes the state of affairs

in the following terms : ' While numerous investigations had