STRUCTURE.] ALBUMEN OF LEGUMINOUS PLANTS. 57 



the embryo-sac becomes changed into a part of the 

 embryo ; but in Lupinus only a part of the tube becomes 

 organised with the embryo, the remaining portion 

 forming a little cord-like body, called by Mirbel the 

 suspensor. As the embryo-sac extends, it forms cells 

 out of the mucous and saccharine solution in its inside, 

 the cells being developed around the cytoblasts in the 

 manner described by Schleiden. At the same time this 

 cellular tissue is forming the embryo increases in size, 

 and either absorbs this or presses it more or less together ; 

 in the latter case it is the seat of the deposit of albumen. 

 This is often the case, and in most instances the nucleus 

 is entirely absorbed. Hence the albumen of Leguminous 

 plants is endosperm; its greater or smaller thickness 

 depends on the greater or smaller size of the embryo. 

 In the whole family there is a very decided fluctuation 

 in the presence and quantity of this albumen ; so that 

 the suggestion of Braun to distinguish the genera of 

 Mimosea3 by it, is quite untenable. In fact there are 

 some very good genera, as Lupinus, in which some 

 species have it, and some have none. Lupiuus tomentosus 

 and L. macrophyllus both have albumen, L. tuberosus 

 none. In Ononis altissima, it is scarcely to be seen, 

 whilst in O. aculeata it is very abundant. JEschynomene 

 fluminensis has a maximum, whilst JE. podocarpa has a 

 minimum. Many more examples would undoubtedly 

 occur in large genera, as Trifolium, &c. In Acacia some 

 species have abundance, others none. But if the existence 

 of albumen fluctuates, much more do its relative quantity 

 and its relative position to the embryo. Its development 

 is least decisive in the whole family on the edges of the 

 cotyledons ; in Papilionacese least at the hilum and in 

 greatest quantity between the radicle and cotyledons, 

 and in the commissure between the cotyledons ; in both 

 of which places it may be beautifully seen in Scorpiurus 

 sulcatus, yet it is sometimes wanting here when it 

 appears on the sides of the cotyledons. The quantity of 

 albumen has been supposed to be in an inverse propor- 

 tion to the size of the plumule, but this is not a rule, 



