ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
549 
BOTANY. 
A. GENERAL, including the Anatomy and Physiology 
of the Phanerogamia. 
a. Anatomy. 
Cl) Cell-Structure and Protoplasm. 
Histology of the Vegetable Nucleus.* — From a study of the phe- 
nomena connected with the sickle-stage of the nucleole in vegetable 
cells, Dr. B. Lidforss comes to a conclusion adverse to that of Strasburger 
and Humphrey, that it is an artificial phenomenon, due to the mode of 
treatment. Out of 21 species examined, belonging to three different 
natural orders, he finds it in 17 ; in the remaining four there is at the 
corresponding stage only a movement of the nucleole towards the peri- 
phery of the nucleus. In any one ovary either all or none of the 
embryo-sac nuclei showed the sickle structure of the nucleoles ; it was 
exhibited also with the most various fixing materials. As far as the 
embryo is concerned, it was observed only in the primary embryo-sac 
nucleus when mature; not in its daughter-nuclei, nor in those of the 
surrounding tissue of the nucellus. The author records also the occur- 
rence of the sickle-stage in the nucleoles of pollen-mothcr-cells, where it 
is probably a widely distributed phenomenon. 
To elucidate the question of the chromatophily of the vegetable 
nucleus, Dr. Lidforss cultivated pollen-tubes of Agapanthus umbellatus 
in distilled water and in sugar-pepton solution. He found, in the latter 
case, the tubes to be filled, from their base to their apex, by a dense 
mucilage, composed of proteids, presenting, therefore, a favourable con- 
dition of nutrition for the nuclei. The vegetative nucleus and the 
cytoplasm were then found to be strongly erythrophilous ; while the 
generative nucleus was distinctly cyanophilous. The cyanophilous 
reaction of the male sexual cells in Angiosperms cannot, therefore, be 
dependent, as has been suggested, on a deficient supply of nutriment. 
Structure of the Nucleus.^ — Sig. F. Cavara has studied the structure 
and function of the nucleoles, and their relation to the chromosomes 
during and after karyokinesis. Resting nuclei are of two kinds — those 
which for the moment only are not dividing, and those which are no 
longer capable of division ; these latter are found in sieve-tubes, vessels, 
and in all elements which are not capable of division but which manifest 
an active growth. The nuclei are then very large, and contain largo 
nucleoles. In embryo-sac nuclei the nucleoles exhibit a special 
structure. 
Specially important is the study of the phenomena which immediately 
precede division ; the nucleoles are not expelled, but break up and are 
absorbed by the nuclear threads. 
The nucleoles consist of an inner homogeneous slightly stainable 
substance (plastin or py renin), and an outer stainable substance, varying 
in density and often spongy, comparable to chromatin. During division 
* Act. Univ. Lund, xxxiii. (1897) 29 pp. and 1 pi. (German), 
t Atti 1st. Bot. R. Univ. Pavia, v. (1898) 49 pp. and 2 pis. See Bot. Centralfci., 
lxxiv. (1898) p. 239. 
2 p 2 
