SEED. 



105 



577. Pea seed (mag.), deprived of 

 half its integument and one of 

 its cotyledons. 



close to shelter the seeds, but protect them by closely overlapping each other until 

 ripe. They are sometimes woody, when they form either a conical spike (Pine, fig. 

 574), or a globular head (Cypress, fig. 575) ; when fleshy and connate, they simulate 

 a drupe (Juniper, fig. 576). 



SEED. 



The seed (semen) of phsenogams is the ovule when fertilized, ripe, and ready for 

 germination; it contains the embryo (embryo, plantula, corculum), which is destined 

 to reproduce the mother-plant. Let us recapitulate the structure of the embryo in 

 the Pea (fig. 577). It is composed of a caulicle (cauliculus, 

 T), a radicle (radicula, E), two cotyledons (cotyledones, c), and 

 a plumule (gemmula, plumula) ; it is enveloped by a double 

 integument, of which the outer (i), or testa (testa), is 

 attached to the hilum (hilus, umbilicus) by the funicle 

 (funiculus, F), which rises from the placenta (placenta, p) ; 

 and the inner (E), or endopleure, } (endopleura) provides a 

 passage for the nourishing juices by the chalaza (chalaza, H), 

 which communicates with the hilum by means of a cord (A), 

 the raphe (raphe). Near the hilum is a small opening (M), 

 the micropyle (micropyle), by which the ovule is fertilized by 

 the pollen. As a general rule, the radicular end of the embryo answers to the 

 micropyle, and the cotyledonary end to the chalaza ; the exceptions to this rule, 

 which are rare, and do not invalidate it, will be specified. 



Relative Positions of Seed and Embryo. It is important to observe that, in the 

 early condition of the ovule, the hilum and chalaza are united ; consequently the 

 raphe does not exist, and the micropyle occupies the opposite, or free end of the 

 ovule; also that 1, the base of the fruit (ovary 2 ), is the point by which this is 

 attached to the receptacle, and its top is the point from which the style springs ; 

 2, the base of the seed is the point by which it is attached to the 

 funicle or placenta, and which is indicated by the hilum ; the 

 top of the seed is the extremity of an imaginary straight or 

 curved line drawn through the axis of the seed. The axis of the 

 ovary is defined in the same manner. 

 The embryo has also its axis; its 

 base is its radicular, and its top its 

 cotyledonary extremity. 



The top of the seed is obvious 

 tne whenever the hilum occupies either 

 t*he extremity of the long axis of the seed, 

 in| as i s usually the case (Nettle, fig. 

 578 ; Sage, fig. 579 ; Chicory, 580) ; 

 the hilum is placed at the middle of the long axis of the seed 



PL 



578. Nettle. 



Achene cut vertically (mag.), 

 showing one of the large 



the top of the ovary. 

 but sometimes 



Gr. 



579. Sage. 



Achene cut vertically 



(mag.), ov, ovary ; 



Gr, seed. 



1 Sometimes called legmen. ED. 



2 Throughout this section tho authors speak of the 



seed in relation to the ovary, where we should say 

 carpel or fruit. ED. 



