294 



EMBEYOGENY IN GYMNOSPEEMS. 



into the substance of the nucleus. The four elongated pro-embryonic 

 cells (fig, 526, 1) now appear as isolated suspensors (fig. 526, 2), 

 and the cell at the end of each suspensor becomes an embryo, g. 

 There are thus four times as many rudimentary embryos as there are 

 corpuscles. Usually one of these only becomes developed as the 

 embryo of the ripe seed. 



Fig. 524. 



Fig. 626, 



Fig. 625. 



In many points this process resembles what takes place in Lyco- 

 pods. The anthers of Gymnosperms may be considered as corresponding 

 to the microsporangia, and the grains of pollen to the microspores. 

 Certain cells in the anther may represent the prothaUus, while a cell 

 forming the poUen-tube may be the antheridium. The embryo-sac 

 in Gymnosperms may be reckoned equivalent to the macrospores, and 

 the endospermal cellular development may be analogous to the pro- 

 thaUus produced in the large spore of Selaginella (see page 278). 

 The prothaUus in some Ferns, as Ophioglossacese, is produced inside 

 the spore, whUe in others it grows out from it in the form of a green 

 expansion, bearing both antheridiaand archegonia (fig. 507, p. 280). 



Emhryogenic process m Angiospermous Flowering Plants. 



In the case of Angiospermous Phanerogams, the pollen-grains 

 (fig. 527 gp) are discharged from the anther, and are applied to the 

 stigmatic surface of the pistil (fig. 527 ps), either directly or by the 



Fig. 524. Nucleated ceUs of what Hofmeister calls the pro-embryo, in tlie ovule of the 

 Weymouth Piae {Pinus Sirdbim). The cells are pushed downwards into the ceUular tissue 

 of the nucleus hy the elongation of the upper ceils, which finally form the suspensor. 

 Fig. 525. The same pro-emhryonic body in the ovule of the Weymouth Pine, with the lower 

 ceUs pushed farther down by the elongation of the upper suspensory cells. Fig. 526. 

 Suspensors taken from the ovule of the Weymouth Pine [Pymis Strolms): In No. 1 the four 

 suspensors are united. They form a cylinder composed of four elongated cells, »nd at the 

 end, J), are seen some of the lower nucleated cells of the pro-embryo. In No. 2 the suspen- 

 sors have separated, three of them, a, are cut off, and the remaining one, 6, is connected 

 with the embryo, g, at its extremity. 



