404 STUDIES IN SEEDS AND FRUITS 



before the resting state is imposed. All exalbuminous seeds 

 have in a sense been once albuminous, and the distinction 

 which we draw between exalbuminous and albuminous seeds 

 mainly depends on whether the transition occurs before or 

 after the rest-period. The after-ripening of seeds must be 

 often concerned with the change from the albuminous to the 

 exalbuminous condition. That which happens in the Jasmine, 

 where the albumen is at first copious in the seed and dis- 

 appears when the seed is ripe for germination, occurs with 

 many other plants. It would be quite possible, for instance, 

 in the case of the Ivy (Hederd), as described in Chapter XIX, 

 to describe the seed as albuminous in its first stage and as 

 exalbuminous when about to germinate. The interposition 

 of the rest-period in the early portion of a plant's existence 

 is responsible for many false distinctions and many incorrect 

 comparisons. 

 Other diffi- Another difficult point has been already indicated. In the 



poin . resting albuminous seed, as is well known, the embryo may 

 exist in all stages, from that in which it is imperfectly differ- 

 entiated to that in which the plumular leaves are developed 

 and we have a perfect plantlet within the seed. Between these 

 two extremes all gradations occur. Then, again, we have often 

 genera with exalbuminous seeds and genera with albuminous 

 seeds in the same order. Thus with Sapotacese, at first sight 

 the seeds seem very similar in structure. Yet the proportion 

 of albumen may vary in different genera, from that found in 

 Achras^ where it amounts to about 84 per cent, of the kernel's 

 weight, to its condition in Chrysophyllum, where it may range 

 between 20 and 40 per cent, in different species, whilst in 

 Lucuma there is none at all. Of the 222 families of angio- 

 sperms described in the System of Botany of Le Maout and 

 Decaisne, about 18 per cent, possess both albuminous and 

 exalbuminous seeds. 



Dr Goebel in his Organography of Plants (English edition, 

 ii. 262) lays stress on the far-reaching nature of the changes 

 in the form of the embryo arising from the different modes of 



