Highei' Crijptogamia and the Phanerogamia. 449 



searches of R. Brown and Hofmeister have revealed most im- 

 portant facts with regard to the fertihzation of the ovules of 

 the Coniferse, which afford a link connecting the sexual repro- 

 duction of the vascular Cryptogamous plants most closely with 

 that of the Angiospermous flowering plants. But although the 

 processes in the Conifers stand intermediate between those of the 

 Rhizocarpese, &c., and those of the flowering plants, they are so 

 much simpler in the latter that it will make the explanation 

 clearer to take them first. 



Angiospermous Flowering Plants. 



One of the simplest cases is that of Orchis Morio. The ovule 

 springs from the placental surface as a single projecting cell, 

 which by subdivision soon becomes a cellular papilla (the nucleus) 

 composed of a central cell (the embryo-sac) surrounded by a sim- 

 ple cellular layer. The two coats gradually grow up over this, 

 and by the greater elongation of one side the ovule becomes 

 anatropous. The nucleus meanwhile loses its cellular coat, ap- 

 parently by absorption, and appears as a large oval sac inclosed 

 in the coats, consisting in fact merely of an embryo-sac. In the 

 apex of this, about the epoch when the pollen falls upon the 

 stigma, three cellules {embryonal vesicles) make their appearance 

 at the upper end of the embryo-sac, formed apparently by free 

 cell-formation around a globule of protoplasm. The pollen- 

 masses on the stigma send down pollen-tubes which traverse the 

 conducting tissue of the style and make their way to the pla- 

 centas, where they enter ordinarily singly (sometimes more than 

 one) into the micropyle canals of the ovules, and come in con- 

 tact with the outside of the apex of the embryo-sac, immediately 

 above where the embryonal vesicles lie ; but the pollen-tube does 

 not penetrate the embryo-sac (PI. XVII. F. fig. 1, 2, 3) . Soon after 

 the pollen-tube has reached the embryo- sac, one (very rarely 

 two) of the embryonal vesicles begins to swell, becomes divided 

 by a cross septum into two cells (F. fig. 4, 5), and while the 

 upper one grows out in a filamentous form through the micro- 

 pyle, by a continued process of cell-division, the lower cell en- 

 larges and divides repeatedly so as to form a cellular globule, the 

 embryo (F. fig. 6), which in this plant does not go on to produce 

 a cotyledon and radicle, as in most other cases. The filamentous 

 prolongation, the use of which is not evident, but which seems 

 analogous to the suspensor presently to be mentioned, meanwhile 

 decays away. 



In other cases the details of the process are considerably mo- 

 dified. In the Cruciferse and Scrophulariaceae for example, the 

 embryo-sac is a large cavity in the substance of a cellular nu- 



