2 THE CoMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
size of the materials makes any other than morphological evidence 
difficult to obtain. For example, it is argued from appearances 
that enzymes or at least zymogens are present in the young endo- 
sperm, though that such is actually the case is not proven. Since, 
however, such substances have been shown to be present and have 
been extracted from, e. g., the young date seedling * and since the 
action of the sucking organ of that plant on the hard endosperm 
is due-to the ability to secrete the zymogens of a cellulose-dissolv- 
ing ferment, we have a working basis for such interpretation 
The position here assumed that morphology must be regarded 
from a physiological point of view is the one emphasized in 1879, 
by M. Treub in the introductory part of his ** Notes sur l'embryo- 
genie de quelques Orchidées," t where he expressed the hope that 
the readers of his paper would agree “que la manière dont les - 
embryons absorbent les substances plastiques mérite certainement 
d'attirer l attention, et sourtout d’être élucidées lors de recherches 
embryogéniques.” That this point of view was not new with him, 
Treub took pains, in a detailed historical treatment, to indicate, 
though it remained for him to adduce the mass of evidence, em- 
bodied in the rich work above referred to, which completely sub- 
stantiates the value of his position. To this historical review the 
reader is referred for an account of the growth of our knowledge 
of the suspensor. The succeeding part of the “Notes” deals 
with the origin, structure and function of the suspensor in eleven . 
genera, including nineteen species of the Orchidaceae, in which 
forms the suspensor is shown to build up for the most part elab- 
orate structures of a haustorial character which serve to absorb 
nutritive substances to be used by the embryo proper in its devel- 
opment. These structures, which attain the highest degree of 
specialization in Herminium monorchis, Phalaenopsis grandiflora 
and Stanhopea oculata, here take the form of tubes (“boyaux ”) 
which penetrate into the surrounding tissues of the ovule. 
Two years later L. Guignard} (81) published an account of his 
quite thorough studies on the embryology of the Leguminosae, in 
* F. C. Newcombe. Cellulose Enzymes, Ann. Bot. 13: 49. 1899. 
T Nat. Verh. d. K. Akad. van Wet. و1‎ 1879 
t Recherches d’ ne en Mee ay Embryologie des legumineuses. 
Ann. sc. nat. Bot. VI. 12: 5-166 
i 
