552 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
an active part in the contraction ; in many Dicotyledons the parenchyme 
within the vascular system appears also to have its share in the process. 
The power of contraction may he confined to roots of a particular order, 
or to those produced at one time only of the year. They may be found 
in some species of a genus and not in other closely allied species. The 
orders in which they have at present been found most frequently are the 
Liliaceae, Irideae, Amaryllideae, and Araceae. 
Root of Suaeda and Salsola.* — M. G. Fron reports the results 
of an examination of the structure and development of the roots of 
species of these genera of Chenopodiaceae, anomalous from the develop- 
ment at a more or less early period of a generative fibro vascular layer 
in the pericycle. He states that the root, when young, presents an 
asymmetry of structure, which is exhibited from the earliest formations, 
and is developed further in the secondary formations, especially in those 
which are anomalous. 
(Edema in Roots of Salix.f — In the roots of Salix nigra , growing in 
water, Mr. H. v. Schrenk finds, in the winter, peculiar structures pre- 
senting a superficial resemblance to lenticels, but differing from them in 
structure and function. They consist of a collection of cells elongated 
radially, and in some cases bursting the epiderm. They appear to be 
formed from a very strong absorption of water in consequence of an ab- 
normally high temperature, which was unable to escape in the ordinary 
way from the absence of transpiring leaves. 
j3. Physiology. 
(1) Reproduction and Embryology. 
Embryogeny and Fertilisation in Lilium.J — Prof . 1 J. M. Coulter, 
Mr. C. J. Chamberlain, and Mr. J. H. Schaffner have followed out the 
development of the sexual cells and the process of impregnation in several 
species of Lilium , especially L. pliiladelpliicum. The following are some 
of the more important points noted : — 
In the development of the embryo-sac, a single large hypodermal 
archesporial cell makes its appearance very early, and there is no evidence 
of the cutting off of a tapetal cell. The sequence of cell-divisions usual 
in Angiosperms is entirely suppressed, and the archesporial cell develops 
directly into the macrospore or embryo-sac. The persistence of the 
spindle-fibres is a common phenomenon in the embryo-sac divisions, and 
often helps to indicate the shifting of the freed nuclei. When the 
pollen-tube has reached and passed the synergids, it comes under the con- 
trol of an influence powerful enough to bend it sharply towards the 
oosphere. The first division of the oosperm is always transverse, re- 
sulting in a small apical cell and a comparatively large and somewhat 
vesicular basal cell. The tissue of the suspensor is erythrophilous as 
compared with the embryo, showing its close relation to nutritive sup- 
plies. In the development of the endosperm, the sexual and polar pairs 
of nuclei were observed to fuse simultaneously ; but when division begins 
the endosperm nuclei divide more rapidly than the cells of the embryo. 
In their early spirem-stages the nuclei of the mother-cells of the 
* Comptes Rendus, cxxv. (1897) pp. 366-8. 
f Bot. Gazette, xxiv. (1897) pp. 52-4 (2 figs.), 
i Op. cit., xxiii. (1897) pp. 412-52 (8 pis.). 
