THE SEED. 153 



The seed remains attached to the placenta of the fruit, until 

 mature, by the funiculus, from which it ultimately separates by an 

 articulation, so that a scar is left, called the hilum. 



The direction and position of the seeds in the cells of the fruit, as 

 well as the modes of curvature, indicated externally by the relative posi- 

 tions of the hilum (fig. 811, a), micropyle (b), chalaza (d), and raphe (c), 

 are the same as in the case of the ovule ; and the same terms are made 

 use of in describing their peculiarities. 



The face of a seed is the side or edge turned towards the placenta from 

 which it arises. 



The direction of seeds may differ from that of the ovules, by alteration 

 in the shape of the ovary, abortion of ovules, &c. It may be noted that 

 anatropous ovules normally have the raphe next the placenta if ascending 

 or suspended, so that the raphe indicates the face. 



Parts of the Seed. The seed consists of the proper body of the 

 seed and its integuments, to which in some cases are added appen- 

 dages of various kinds. 



The outer coat of the seed, called the testa, completely encloses 

 it, marked, however, by the microscopic orifice of the micropyle, 

 and by the hilum, or scar of the funiculus. The testa presents the 

 greatest possible variety of conditions of texture, from membra- 

 nous, horny, woody, or bony hardness, on the one hand, to a 

 leathery or soft, pulpy condition on the other. The dry forms 

 frequently exhibit beautifully regular markings, such as minute 

 ridges, reticulations (Poppy, Silene, &c.), spines (Stel- 

 laria, &c.) ; or the margins are produced into sharp 

 edges or broad wings (Bignonia, Finns, fig. 312) ; or it 

 bears a crown of hairs, or coma, at one end, as in Epi- 

 lobium, Asclepias, &c. ; or it is completely covered with 

 long hairs, as in the Cotton plant : while in various 

 Polemoniacea?, Labiatae, &c.(Collomia &c.) it is clothed 

 with microscopic hairs, which expand elastically and 

 dissolve into a kind of mucilage when wetted. Some- 

 times the testa is loose, and forms a kind of sac around winged seed 

 the body of the seed, as in Orchidacese, Pyrola, &c. Pme * 



The inner integument, the tegmen or endopleura, is not generally 

 distinguishable ; when it is, it is usually whitish and delicate. 



The reference of the integuments of the seed to their elements in the 

 ovule is a subject of great complexity, since there appear to be no rules 

 as to what regions of the ovule, from the nucleus outward, shall remain 

 distinguishable or enter into the composition of the coats. The testa is 

 commonly formed of the primine and secundine (p. 137) of the ovule con- 

 joined. The tegmen seems to originate sometimes from the secundine, 

 sometimes from the substance of the nucleus, &c. Small indehiscent fruits, 

 such as the achaenia of Ranunculus (h'g. 313) or of Borages (tig. 282, p. 145), 



