TfTR EMBRYO AND rOTYLEDONS. 219 



life and organization of the future plant originate, as 

 we have already explained, p. 88. In some seeds it 

 is much more conspicuous than in others. The Wal- 

 nu*, t le Bean, Pea, Lupine, &c., show the Embryo 

 in netft'Ction. I* s internal structure, before it begins 

 to vegetate, is observed by Gaetner to be remarkably 

 siiuple, consisting of an uniform medullary substance, 

 enclosed in its appropriate bark or skin. Vessels are 

 formed as soon as the vital principle is excited to ac- 

 tion, and parts are then developed which seemed not 

 previously to exist, just as in the egg of a bird. In 

 position, the Embryo is, with respect to the base of 

 the whole flower or fruit, either erect, as in the Dan- 

 delion and other compound flowers, reversed as in the 

 Umbelliferous tribe, or horizontal as in the Date 

 Palm, f. 199 b, Gcertner, t. 9. In situation it is 

 most commonly within the substance of the seed, 

 and either central as in Umbelliferous plants, or ex- 

 centric, out of the centre, as in Coffee ; in Grasses 

 however it is external. Its direction is either straight, 

 curved, or even spiral, in various instances. The 

 Embryo of seeds that have a single cotyledon, or none 

 at all, is peculiarly simple, without any notch or lobe, 

 and is named by Gasrtner Embryo monocotyledoneus. 

 Cotyledones, the Cotyledons or Seed-lobes, are im- 

 mediately attached to the Embryo, of which they 

 form, properly speaking, a part. They are commonly 

 two in number, f. 7 ; but in Pinus, and Dombeya, 

 ihe Norfolk Island Pine, they are more, y^ 3, as al- 

 ready mentioned, p. 90. When the seed has suffi- 

 ciently established its root, these generally rise out of 



