18 THE COMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
with its suspensorial haustoria, to which it is attached by the short 
row of disc-shaped cells, comes to lie entirely within the now large 
mass of endosperm (Pl. 4, Figs. 9, 10). The structures above 
described are probably to be regarded as an adaptation for the 
ready absorption of food for the rapid growth of the embryo. 
The shortness of the cells of the embryonal region of the sus- 
pensor favors the passage of food tothe embryo. Whether or not 
the embryo is capable of absorbing food through its own surface is 
a question which I am unable to answer at this time.  Koorders 
(92), working on Tectona, found that the embryo till the com- 
pletion of the ** Kogelstadium ” possessed cuticularized walls, thus 
preventing the absorption of food. If this be true of Vaillantia 
and its close relatives, we have a complete explanation of the sig- 
nificance of the haustoria. But even if the embryo is not cuticular- 
ized, it is not improbable that the amount of absorbing surface on 
the embryo proper alone is insufficient for its rapid development, 
and it may be that in this lies the explanation of many features in 
other forms not yet cleared up. For example, I have found that 
the basal cell in Capsella, figured years ago by Hanstein, and 
copied in almost every text-book, actually pushes its way into the 
adjacent tissue of the inner integument in the same manner that 
the embryo-sac itself, by its growth, in many cases encroaches 
upon the surrounding tissue. This fact indicates that the sus- 
pensor, in forms in which it reaches so pronounced a development, 
as in the Cruciferae, Tropaeolum and others, is of importance in 
absorbing nourishment, an opinion which we must credit to Meyen 
(39).* I believe this action of the suspensor in the surrounding 
tissue to be correlated with the rapid growth of the embryo in 
Capsella. Before drawing any conclusions of this kind, however, 
it will be necessary to obtain many more data. 
There can be little doubt that the rapid development of seeds 
is an important adaptive feature, and the study of structures which 
are correlated with this ability will be a fertile field for further 
study. Such haustorial structures as those found in the Orchida- 
ceae may be correlated with the meagre integument which means 
a meagre store of food immediately at hand. 
The further development of the embryo, which brings the 
* Neues system der Pflanzen-Physiologie 3: 331. 18 39. 
