i)f the External Coatings of Seeds. 



%11 



consistent with the operation of those laws, must be held to be 

 founded in misconception. 



2. Every tunic of the vegetable ovule is formed of three ele- 

 mentary parts ; its outer and inner surfaces (epiderm and endo- 

 derm) consisting of a layer of very consolidated cells compacted 

 with and enclosing a great mass of looser cellular tissue (meso- 

 derm), from which they are not separable, as distinct pellicles, 

 without laceration of their surfaces : these inner cells are filled 

 with various substances that constitute pleurenchyma, &c., des- 

 tined for the protection of the nucleus. 



3. No communication of vessels can pass from the mesoderm 

 of one into the mesoderm of another tunic, except through the 

 common point of their origin. 



4. There the mesodermal tissues of all are united, and are 

 connected or are in communication with the secreting surface 

 of the placenta; and I have distinguished by the name of gan- 

 gylode this common point of junction of the coats and nucleus 

 of the ovule. 



5. When an ovule is erect, the gangylode is necessarily co- 

 incident with the point of attachment of the ovule to the pla- 

 centa, and here all the nourishing vessels terminate ; consequently 

 there will be no future indication of the presence of any raphe 

 in the tissues of the seminal tunics. 



6. When the position of an ovule is changed by the act of 

 anatropal inversion, the gangylode, or future chalaza in the seed, 

 becomes far removed from the point of its prior attachment to 

 the placenta ; but an intimate communication is still maintained 

 between them by an extension of a portion of the placenta (which 

 I have called the placentary sheath) carrying with it and en- 

 closing the nourishing vessels which constitute the future raphe 

 in the seed. This placentary sheath, though confluent with the 

 outer tunic of the ovule, is still a distinct formation ; and no 

 organic connexion, either then or afterwards, exists between 

 their respective mesoderms, except through the medium of the 



Fig. 1. Fig. 2. 



gangylode. Thus, in the annexed longitudinal and transverse 



