ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
437 
BOTANY. 
A. GENERAL, including the Anatomy and Physiology 
of the Phanerogamia. 
a. Anatomy. 
(1) Cell-structure and Protoplasm. 
Development of the Achromatic Nuclear-division Figure in Vege- 
tative and Reproductive Tissues.* — Dr. B. Nemec insists on the im- 
portance of the difference in the phenomena of division of the nucleus 
exhibited by the vegetative and reproductive (sporogenous) tissues in the 
higher plants, especially in connection with the uniformity of the phe- 
nomena associated with the reproductive processes in animals and plants. 
The (hypochromatic) reduction of chromatin characteristic of repro- 
ductive cells occurs only in exceptional and pathological conditions of 
vegetative cells. But the stage of the mother-cell nucleus known as 
synapsis, in which the chromatin threads on one side of the nuclear space 
(usually surrounding the nucleole) appear contracted on one side, is, in 
the opinion of the author, not confined to reproductive cells. It occurs 
occasionally in vegetative cells, where the development of the chromatin- 
threads can be followed out to a form identical with the synapsis stage. 
A further difference is exhibited in the development of the achro- 
matic nuclear-division figure. In the vegetative cells (apex of the stem 
and root of Equisetum ), the bipolar structure can be recognised from the 
commencement of the division of the nucleus ; while in the formation of 
the spore-mother-cells it is only a later and secondary phenomenon. In 
the vegetative tissue of Allium the achromatic figures are also bipolar 
from the first. 
Multinucleated Vascular Elements in the Dioscoreacese.j — Sig. R. 
Pirotta and Dr. L. Buscalioni describe the occurrence, which they believe 
has not previously been noted, of vessels with a large number of nuclei 
in the species of Dioscoreaceae examined — Tamus communis , and several 
species of Dioscorea. The stem, the leaves, and the root, but not the 
tubers, are distinguished by the presence, in the vascular bundles, of a 
few vessels of a much larger size than the rest. These larger vessels 
originate from rows of cells which are at first rectangular in longitudinal 
section, but which soon greatly exceed the others in length by inter- 
calary growth. At the same time the karyokinetic multiplication of the 
nucleus commences, and proceeds with such rapidity that the nuclei in a 
single cell may amount to one hundred. As in other similar cases, all 
the nuclei in one cell divide simultaneously. The ordinary process of 
karyokinesis is naturally somewhat modified by taking place at the same 
time in so many nuclei crowded into a small space. It is only after this 
that true vessels are formed by the coalescence of the cells. 
Protoplasm and Active Albumen.J — Prof. 0. Loew defends his 
previous conclusions against unfavourable criticism by Pfeffer in his 
* Bot. Central bl., lxxiv. (1898) pp. 1-4 (8 figs.). Cf. this Journal, ante, p. 316. 
f Atti R. Accad. Lincei, vii. (1898) pp. 141-5. 
X Bot. Centralbl., lxxiv. (1898) pp. 5-13. 
