60 EMBRYO COTYLEDONS. [BOOK i. 



Its relative position is determined by the relation it bears 

 to the chalaza and micropyle of the seed ; or, in other words, 

 upon the relation that the integuments, the raphe, chalaza, 

 hilum, micropyle, and radicle bear to each other. If the sacs 

 of the ovule are in no degree inverted, but have their common 

 point of origin at the hilum, there being (necessarily) neither 

 raphe nor chalaza visible, the radicle will in that case be at 

 the extremity of the seed most remote from the hilum, and 

 the embryo inverted with respect to the seed, as in Cistus, 

 Urtica, and others, where it is said to be antitropal. But if 

 the ovule undergoes the remarkable extension of one side 

 already described in speaking of that organ, when the sacs 

 are so inverted that their orifice is next the hilum, and their 

 base at the apex of the ovule, then there will be a raphe and 

 chalaza distinctly present ; and the radicle will, in the seed, 

 be at the end next the hilum, and the embryo will be erect 

 with respect to the seed, or orthotropal, as in the Apple, 

 Plum, &c. On the other hand, supposing that the sacs of the 

 embryo suffer only a partial degree of inversion, so that their 

 foramen is neither at the one extremity nor the other, there 

 will be a chalaza and a short raphe ; and the radicle will 

 point neither to the apex nor to the base of the seed, but the 

 embryo will lie, as it were, across it, or be Tieterotropal ) as is 

 the case in the Primrose. When an embryo is so curved as 

 to have both apex and radicle presented to the hilum, as in 

 Reseda, it is amphitropal. It is, however, becoming customary 

 to apply to the seed the same names as those used in express- 

 ing the modifications of the ovule ; this will probably become 

 the universal practice, and then all terms referring to the 

 position of the embryo will become superfluous. 



In the words of Gartner an embryo is ascending when its 

 apex is pointed to the apex of the fruit ; descending, if to the 

 base of the fruit ; centripetal, if turned towards the axis of 

 the fruit ; and centrifugal, if towards the sides of the fruit : 

 those embryos are called wandering, or vagi, which have no 

 evident direction. 



The cotyledons are generally straight, and placed face to 

 face ; but there are numberless exceptions to this. Some are 

 separated by the intervention of albumen (Plate VI. fig. 11.) ; 



