450 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Leaves of Cycadeae.* — Dr. A. Nestler has examined the structure 
of the leaves in the various genera of Cycadese, especially in reference 
to the distribution of the stomates. With very few exceptions, they 
occur on the under side of the leaf only, and the same is true of the 
rachis. The development of the hypoderm and of the palisade-tissue 
varies in the different genera. Deposits of calcium oxalate occur com- 
monly in thin-walled parenchymatous cells scattered through the meso- 
phyll, especially in the immediate neighbourhood of the vascular bundles 
and fibres of sclerenchyme. 
Vegetative 1 Organs of the Taccacese and Dioscoreaceae.j— M. C. 
Queva enters into this subject in great detail, taking as types of the 
Taccaceae Tacca pinnatifida and Ataccia cristata. In the former the 
tuber makes its first appearance as a slight swelling at the base of the 
second leaf of the seedling. 
In the Dioscoreaceae he distinguishes three kinds of tuber, those 
belonging to the type of Tamus , of Helmia , and of Dioscorea, in 
addition to the rhizome of the type of Dioscorea quinqueloba. The tuber 
of Testudinaria elephantipes belongs to the Tamus type. 
Anatomy of Typhacese.f — Sig. F. Saccardo discusses the morphology 
of the vegetative and reproductive organs of TypJia and Sparganium, and 
concludes that there is less essential difference in the floral structure 
than was assumed by Engler. The differences, on the other hand, 
between these genera and the Pandanaceae are much more deeply seated, 
especially in their histological structure. The Pandanaceae are un- 
doubtedly an ancestral type from which Sparganium is descended, and 
Typha again from the latter. 
B. Physiology. 
(1) Reproduction and Embryology. 
Part taken by the Antipodals in Polyembryony.§ — Herr S.Tretjakow 
has studied the phenomenon of polyembryony in Allium odorum. Besides 
the central nucleus of the embryo-sac, the ovum-cell, and the two 
svnergids, there are three antipodals, one of which is larger than the 
other two, and resembles the ovum-cell in the arrangement of its contents, 
while the other two more resemble the synergids. Polyembryony results 
from the development of one or all of the antipodals as well as of the 
ovum-cell. This appears to be parthenogenetic, the author never having 
been able to detect any impregnation of the antipodals by the pollen- 
tube. He was able, however, to follow out the formation of an eight- 
celled body from the division of the nucleus, the process being strictly 
analogous to that of an ordinary embryo. A process of nuclear division 
was also observed in one of the synergids. 
The author regards the antipodals as homologous with the vegetative 
cells of the female pro-embryo of some ferns, for the development from 
them of embryos is analogous to the phenomenon of apogamy in ferns. 
* Jahrb. f. wiss. Bot. (Pfeffer u. Strasburger), xxvii. (1895) pp. 341-68 (4 pis.). 
t ‘ Rech. sur l’anat. de l’appareil veg. des Taccacees et des Dioscorees,’ Lille, 
1894, 457 pp., 18 pis. and 70 2 figs. See Bot. Centralbl., Ixi. (1895) p. 401. Cf. 
this Journal, ante, p. 69. J Malpighia, ix. (1895) pp. 3-30 (6 pis.). 
§ Ber. Deutsch. Bot. Gesell., xiii. (1895) pp. 13-7 (1 pi.). 
