350 



ORGANOGRAPHY. 



reference to Cniciferous Plants (see Cruciferge), which are com- 

 monly arranged according to the manner in which the different 

 parts of the embryo are folded, and their relative positions to 

 each other. 



Having now described the general characters of the mono- 

 cotyledonous and dicotyledonous embryo, we have, in the last 

 place, to allude briefly to the relation which the embryo itself 

 bears to the other parts of the seed, and to the pericarp or loculus 

 in which it is placed. 



Relation of the Embryo to the other Parts of the Seed, and to the 

 Fruit. — In the first place with regard to the albumen. It must 

 necessarily happen that when the albumen is present, the size 

 of the embryo will be in the inverse proportion to it ; thus in 

 Grasses {fig. 687) we have a large deposit of albumen and 

 but a small embryo, while in the Nettle {fig. 757), the embryo 

 is large and the albumen small. The embryo may be either 

 external to the albumen, and thus in contact with the integu- 

 ments, as in Grasses {fig. 687), in which case it is described as 

 external; or it may be surrounded by the albumen on all sides, 

 except on its radicular extremity, as in the Pansy {fig. 752), 

 when it is internal. Sometimes the end of the radicle, as in the 

 Coniferaj, becomes united to the albumen, and can no longer be 

 distinguished. 



The embryo is said to be axile or axial when it has the same 



Fig. 757. 



Fig. 758. 



Fig. 759. 



Fig. 757. Vertical section of the achroniuni of a Nettle, containing a single 

 seed. «. Integuments of the seed. p/. Placenta, r. Kodicle. sr. Stigma. 

 . Fig. ir,». Vertical section of the fruit of the Dock lyiumtvr). or. Peri- 

 carp, niic Mieropyle. ;>'. Embryo towards one side of the albumen, alb. 



ch. Chalaza Fig. 7.''>0. Vertical section of the carpel of ilinilnlinjuhiita, 



contniniiii? one seed. <i. IVricurp. .«. Style, c. Pi-riphericiil einhryo with 

 its radicle, r, and cutylcdniis, r. p. Albumen, t. Intcpuments of the seed. 



, Fig. 7(;(). Vertical section of the seed of l.iiclinis iliuica. tc. Intcgu- 



mcats. einb. Embryo ou the outside of the albumen, alb. 



