THE EMBRYO. 311 



in the seeds of Asimina (Fig. 680) and all the Custard- Apple 

 family, it is marked by transverse lines or divisions (caused by 

 inflexions or growths of the inner seed-coat) , giving a section 

 of it either a marbled appearance, or as if it had been slit by 

 incisions : it is then said to be ruminated. 



606. The Embryo, 1 being an initial plantlet or individual of a 

 new generation, is of course the most important part of the seed. 

 To its production, protection, and support, all the other parts of 

 the fruit and flower are subservient. 



607. In an embryo of full development, namely, one in which 

 all the parts are manifest antecedent to germination, these parts 

 are the Caulicle, otherwise called Radicle, the Cotyledons, and 

 the Plumule. (20, 30.) The first is the initial 



axis or stem, a primary internode ; the second 



consists of the leaves of the primar}' node ; the 



third is a beginning of a farther growth which 



is to develop more stem and leaves. Such an 



embryo is usually unaccompanied by albumen, 



having in the course of its growth taken into 



itself (mostly into the cotyledons) the provision 



which in other seeds is mainly accumulated external to it until it 



is drawn upon in germination. 



1 The word Embryo or Embryon was applied to this body in plants by 

 Bonnet (Considerations sur les Corps organise'es),in 1762, and was introduced 

 into systematic botany at about the same time (1763) by Adanson : it was 

 taken up by Gaertner in 1788. Jussieu in the Genera Plantarum (1789) held 

 to the term Corculum (the cor seminis) which came down from Caesalpinus. 



Being the germinal part of the seed, the embryo of the plant, like that of 

 the animal, is in general language often called the Germ. 



FIG. 681. Seed of a Violet (anatropous), enlarged; with hilum or scar (a), rhaplie 

 (6), and chalaza (c) indicated. 682. Vertical section of the same, showing the straight 

 embryo in the axis of the mealy albumen. 



FIG. 683. Vertical section of the (orthotropous) seed of Buckwheat, showing the 

 embryo folded round in the mealy albumen. 



FIG.. 684. Vertical section of the (anatropous) seed of Elodea Virginica, the embryo 

 completely filling the coats. 



FIG. 685. Seed of Delphinium tricorne (anatropous). enlarged; the hilum, the 

 rhaphe, and the chalaza lettered as in Fig. 681. 686. Vertical section of the same with 

 c, the chalaza, rf, the testa, e, the tegmen,/, the albumen, g, the minute embryo near 

 the hilum (a). 



FIG. 687. Embryo of the Pumpkin, with its short radicle and large and flat cotyle- 

 dons, seen flatwise. 688. A vertical section of the same, viewed edgewise. 



