CHAP. II. SEED. 209 



With regard to the quartine and quintine, one of them is 

 occasionally present in the form of a fleshy sac that is inter- 

 posed between the albumen and the ovule, and envelopes the 

 latter. It is what was called the vitellus by Gsertner, and 

 what Richard, by a singular prejudice, considered a dilatation 

 of the radicle of the embryo : to his macropodal form of which 

 he referred the embryo of such plants. Instances of diis are 

 found in Nymphjea and its allies, and also in Scitaminese, 

 peppers, and Saururus. Brown, who first ascertained the 

 fact, considers this sac to be alwaj^s of the same nature and 

 origin, and as the vesicula colliquamenti or amnios of Malpio-hi. 

 The end by which the seed is attached to the placenta is 

 called the hilum or umbilicus (Plate VI. fig. 5. c, 17. e, 11. c, 

 &c.) \ it is frequently of a different colour from the rest of the 

 seed, not uncommonly being black. In plants with small 

 seeds it is exceedingly minute, and recognised with difficulty; 

 but in some it is so large as to occupy fully a third part of 

 the whole surface of the seed, as in the horse-chestnut, Sa- 

 poteae, and others. Seeds of this kind have been called 

 nauca by Gaertner. In grasses the hilum is indicated by a 

 brownish spot situated on the face of the seed, and is called 

 by Richard spilus. The centre of the hilum, through which 

 the nourishing vessels pass, is called by Turpin the omphalo- 

 dium. Sometimes the testa is enlarged in the form of irregu- 

 lar lumps or protuberances about the umbilicus; these are 

 called strophiolcB or carunculce ; and the umbilicus, round 

 which they are situated, i§ said to be strophiolate or carun- 

 culate. Mirbel has ascertained that in Euphorbia Lathyris 

 the strophiole is the fungous foramen of the primine ; and it is 

 probable that such is often the origin of this tubercle : but at 

 present we know little general upon the subject. 



The foramen in the ripe seed constitutes what is called the 

 wicropyle : it is always opposite the radicle of the embryo ; 

 the position of which is, therefore, to be determined without 

 dissection of the seed, by an inspection of the micropyle, — 

 often a practical convenience. 



In some seeds, as the asparagus, Commelina, and others 

 {fig. 185.), there is a small callosity at a short distance from the 

 hilum : this callosity gives way like a little lid at the time of 



