752 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
cell ; in these cases the hypothesis of growth by turgor is excluded. 
The mode of growth of the epidermal cells of the leaves of Pteris serru- 
lata and of some flowering plants, which have wavy lateral walls, appears 
to agree with that of the stellate cells of Juncus. 
Xaryokinesis in Spirogyra.* * * § — Dr. J. W. Moll has made a series of 
observations on the mode of division of the nucleus in the cells of a 
species of Spirogyra (probably S. crassa ). They relate chiefly to trans- 
itional stages between some well-known stages of karyokinesis, and 
appear to indicate that the process is still more complicated than has 
been hitherto supposed. The observations lead to the conclusion that 
in the resting nucleole there are one or more threads which tenaciously 
retain the staining reagents, and cause a skein-structure ; and that the 
nucleole always contains a certain number of minute vacuoles. Chro- 
matic substance does not exist to any appreciable amount outside the 
resting nucleole ; in the stage of the nuclear plate it appears exclusively 
in the twelve nuclear segments. The phenomenon termed by Flemming 
heteropoly certainly occurs in Spirogyra. 
Average Size of Cells.f — Herr E. Amelung has made an elaborate 
series of measurements of the average size of the cell in different plants 
and parts of plants, and has arrived at the following general con- 
clusions : — Organs of different size, but of the same description, belonging 
to the same individual, consist of cells of the same, or of nearly the same 
size ; the size is generally smaller in aquatic than in land plants. 
The largest tissue-cells observed were those of the stem of Impatiens 
glandulifera i 0*79 by 0*18 mm. Pollen-grains of anemophilous are 
generally smaller than those of entomophilous flowers. 
Formation of the Cell-wall in the Hairs of Lavatera. — Dr. C. 
Acqua describes the aerial hairs of Lavatera cretica as being unicellular, 
the cell-wall at the apex being thickened so as to form a cap of consider- 
able thickness. This thickened portion of the cell-wall is distinctly 
laminated, and the author has determined with certainty that the layers 
of greater and less refracting power are formed separately from portions 
of the protoplasm more or less rich in microsomes. 
C2) Other Cell-contents (including- Secretions). 
New Vegetable Nuclein. § — M. P. Petit has extracted from the 
embryo of the barley-grain a new vegetable nuclein containing iron, 
with a percentage composition, given as C 43*18, H 6*64, N 12*86, 
Ph 1*11, Fe 0*195, ash 6*2, Si 3*2, O (by difference) 31*1. It differs 
from the animal nucleins in containing no sulphur. The chemical and 
physical properties of the substance are given in detail. The author 
thinks it probable that an analogous substance is contained in the soil. 
Ferment of the Pine-apple. || — Mr. E. H. Chittenden states that the 
ripe pine-apple contains a very powerful proteid-digesting principle, and 
the juice also possesses in a remarkable degree the power of curdling 
* Verhandl. Kon. Akad. Wetensch. (Amsterdam), 1893, 36 pp. and 2 pis. (English). 
t Flora, lxxvii. (1893) pp. 176-207. 
t Atti R. Aecad. Lincei, 1893, pp. 154-8. 
§ Comptes Rendus, cxvi. (1893) pp. 995-7. 
II Trans. Connecticut Acad. Arts and Sci., viii. (1893) pp. 281-308. 
