278 SKED OR MATUKE OVULE. 



called embryotega (tego, I cover.) The fibro- vascular bundles, from 

 the placenta pass through the funiculus and reach the seed, either 

 entering it directly at a point called the omphalode (o'^oAo?, navel,) 

 which forms part of the hilum, or being prolonged between the outer 

 and inner integument in the form of a raphe, and reaching the chalaza 

 or organic base of the nucleus, where a swelling or peculiar expansion 

 may often be detected, as in Crocus. In fig. 480, the spiral vessels, 

 r, are seen entering the cord, f, passing through the hilum, A, forming 

 the raphe, r, between the testa, t, and endopleura, m z, and ending in 

 the chalazal expansion, c. So also in fig. 484, where f is the funi- 

 culus, r the raphe united to the hilum and chalaza, c, whence vessels, 

 v, penetrate the seed. In some seeds, as Narthecium ossifragum, the 

 vessels are said not to appear till after fertilization, and in Habenaria 

 viridis, none have been detected. The chalaza is often 

 of a different colour from the rest of the integuments. 

 In the Orange, it is of a reddish-brown colour. Some- 

 times, however, its structure can only be recognized 

 by careful dissection. It indicates the cotyledonary 

 extremity of the embryo. The hilum and chalaza 

 may correspond, or they may be separated from each 

 other and united by the raphe (fig. 484). The raphe 

 is generally on the side of the seed next the ventral suture. 



584. The positions of the hilum, micropyle, and chalaza, are of 

 importance in determining the nature of the seed. The hilum is the 

 base of the seed, and the micropyle its apex, while the chalaza is the 

 organic base of the nucleus. The hilum and chalaza may correspond, 

 the micropyle being at the opposite extremity, and then the seed is 

 orthotropal (ojdoj, straight). The seed may be curved so that the 

 micropyle is close to the hilum, and the chalaza, by the growth of the 

 seed on one side, may be slightly removed from the hilum, then the 

 seed is campylotropal (xa^Tiixo?, curved). The micropyle may be 

 close to the hilum, and the chalaza in the progress of development 

 may be removed to the opposite end, then the seed is anatropal 

 (Tg7na, I reverse).* 



585. The position of the seed as regards the pericarp, resembles 

 that of the ovule in the ovary, and the same terms are applied erect, 

 ascending, pendulous, suspended, curved, &c. (figs. 423, 424, 425, 

 426, 420.) These terms have no reference to the mode in which the 

 fruit is attached to the axis. Thus the seed may be erect while the 

 fruit itself is pendent, in the ordinary meaning of that term. The part 

 of the seed next the axis or the ventral suture is its face, the opposite 

 side being the back. Seeds exhibit great varieties of forms. They 



* See T 467, where these terms are more fully explained when treating of the ovule. 

 Fig. 484. Seed of the Hazel. /, Funiculus. r, Raphe. c, Chalaza. n. Veins spreading in a 

 radiating manner over the integuments of the seed. 



