332 



ORGANOGRAPHY. 



enclose the nucleus except at its apex {fig. 718). The inner 

 coat is at first seen to project beyond the outer, but the latter 



ultimately reaches and en- 

 Fig. 717. Fig. 718. closes it. The inner coat 



is termed the secundine, s, 

 and the outer the primine, p. 

 Schleiden and some other 

 botanists call the secun- 

 dine, the inf eg amentum pri- 

 mum internum, and the pri- 

 mine, the infegnmentum se- 

 cundum externum; which on 

 the whole are the best terms, 



Fig. 717. Ovule of the Walnut iJwjlans .^^ ^\^Qy indicate, not Onlv 

 rcf/ta). n. Nucleus, s. Coat covering the nu- •' c ^ i 



cieus, except at the foramen, cMft. — Hg. the order oi development 



718. Ovule of species of PoZ^/ffouMHi./ End ^f t}-,^ ^oatS, but also their 

 of ovule attached to placenta, p. Pnmine. , . '. . ^^ , 



.s. Secundine. ex. Exostome. end. Eiido- relative position. Other 



^*"'"*^- German botanists, again, 



also following the order of development, term the inner coat /?n'- 

 mine, and the outer secundine, tluis reversing the names as com- 

 monly applied in this country. The orifice left at the apex of the 

 nucleus, as in the former instance where only one coat was 

 present, is called the foramen or micropyle. The openings in 

 the t\vo coats commonly correspond to each other, but it is 

 sometimes found convenient to distinguish these by distinct 

 names ; thus that of the outer, is called the exostome, ex, that 

 of the inner, endostome, end. The nucleus and its coat or coats 

 are intimately connected at one point by a cellulo-vascular cord 

 or layer, called the chalaza {figs. 719 and 720, ch) ; at the other, 

 parts of the ovule they are more or less distinct. This chalaza is 

 the point where the vessels pass from the placenta or funiculus 

 into the ovule for the purpose of aftbrding nourishment to it; it is 

 generally indicated by being colouied, and of a denser textui-e 

 than the tissue by which it is surrounded (figs. 7 19 and 720). The 

 chalaza is by some considered as the organic base of the ovule, 

 and the micropyle as the organic apex ; but it is better to speak 

 of the hilum as the organic base of the ovule, and the chalaza 

 as the base of the nucleus. Through the micropyle or organic 

 apex of tlie ovule, the influence of the pollen is conveyed to the 

 cinliryo-sac, as will be hereafter fully described 



Hklation of the Hilum, Chalaza, and Micropyle to 

 EACH oTHKU. — Whcu au ovulc is first devclo])cd, the point of 

 union of its coats and nucleus, called the chalaza, is at the base 

 or liilnin, close to the placenta ; in which case, a straight line 

 wotUd pass from the micropyle through the axes of the nucleus 

 ami its coats to the hilum. In rare instances this relation of 

 parts is preserved throughout its develoiMuent, as in tlie Poly- 

 gonaccjc (fig. 719), &c. ; sucli ovules are termed orthotropous 



