188 VEGETABLE ORGANOGRAPHY. 



more quickly than the latter. Similar observations have 

 not as yet been made upon other dioecious plants, so 

 that it would be imprudent, in the present state of our 

 knowledge, to affirm if these laws be more or less 

 general. 



The weight of seeds is much more capable of being 

 appreciated : in general, ripe and fecundated ones are 

 heavier than water, and this law appears to be universal. 

 Seeds which have not attained maturity, or the embryo 

 of which has not been fecundated, are almost always 

 lighter than water, a practical character which enables 

 all gardeners to distinguish good seeds from bad : it 

 must be remarked that good ones may swim when they 

 retain a stratum of air, confined around them by means 

 of hairs, wings, or cavities which may surround them. 



Section II. 



Of the Spermoderm, or Skin of the Seed. 



The proper skin, envelope, or coat of the seed, is an 

 organ so distinct, that it was very right to give it a 

 name. Richard, from analogy with the word pericarp, 

 proposed that of Perisperm, and afterwards that of 

 Episperm; but these terms do not seem to me to be 

 admissible ; the first, because Jussieu used it in another 

 sense ; the second, because, having no similarity with 

 the sense of the word epicarp, it would produce con- 

 fusion. I have replaced them by the term Spermoderm, 

 which expresses, in one word, the skin or coat of the 

 seed; this envelope exists in every seed, and I cannot 

 admit what Mirbel says of its absence in some ; Gaertner 

 considered it as formed of two membranes, which he 



