322 Corda on the Impregnation of Plants. 



impregnation, even until the embryo has assumed an egg-shaped 

 form, and has increased very considerably in size, becoming at the 

 same time firmer and nearly opaque, (Tab. 44, fig. 22, a' and E.) 

 At this period the embryostome contracts, (Tab. 44, fig. 22, /') the 

 nucule becomes thinner, and being, as well as the secundine (f?,) 

 confined between the growing embryo within, and the primine [cc) 

 without, both these membranes become very much compressed. 

 The pollen-tubes (Tab. 44, fig. 22 a') are at this time very much 

 attenuated and filiform, and so much shrivelled that neither cavity 

 nor contents can be observed ; they are, moveover, so much attenu- 

 ated at the extremity next the embryo-sac that it becomes very dif- 

 ficult to trace them to that body, and demonstrate their connexion 

 with its surface, which is now rough and nearly opaque. 



About this time the pollen-tubes appear to fall away, and, on ac- 

 count of the solidifying of the albumen, it becomes impossible to 

 perceive any vestige of its former presence. 



After having considered the fecundation and the structure of the 

 ovule, I undertook to examine the different integuments of the ma- 

 ture seed. The ripe seed of the Rothtanue [Pinus Abies) is fur- 

 nished with a wing, (Tab. 44, fig. 30, a?, and fig. 33,) the base of 

 which (6) half surrounds the nut ; the upper part, like a fine, thin, 

 separated portion of integuments, forms the wing itself, [t.) This 

 wing is nothing else than the inner skin of the lower part of the 

 inner surface of the scale ; and the line of separation is visible at an 

 early period, (Tab. 44, fig. 21, t,) by which, when the seeds are 

 ripe the cavity of the ovule opens and the formation of the wing is 

 effected. By removing this wing, the nut is seen free from all con- 

 nexion, (Tab. 44, fig. 30 w and 31.) The vestige of an opening is 

 observable at its summit ; (the endostome of the ovule (Tab. 44, fig. 

 31, 32 and 34 e'e',) called the micropyle by Turpin,) perforating 

 the hard covering of the seed (testa) which represents the primine 

 of the ovule, (Tab. 42, fig. 3 ; Tab. 44, fig. 21, 22, and 34, ccc.) 

 Beneath the testa and partly coherent with it, is the inner covering 

 of the seed, (Tab. 44, fig. 34, d,) a brownish skin which represents 

 the secundine of the ovule, (Tab. 42, fig. 3, and Tab. 44, fig. 21, 22, 

 and 34, d, d, d.) Its opening, the endostome (Tab. 44, fig. 34, 

 e^ -\-f^) is firmly connected with the embryostome, (Tab. 44, fig. 

 22/0 of th^ kernel-skin, (nucule,) (Tab. 44, fig. 21 /, 22/, and 

 34/.) In the fecundated ovule and ripe seed there is situated, in 

 and near the orifice of these three iiiteguments, a yellowish, firm 

 and shrivelled body, of a loose texture, which was called by Gsert- 



