ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
399 
Streaming of Protoplasm in Pollen-Grains.* — According to Miss 
H. B. Potter, many pollen-grains — those of the foxglove are a good 
example — are convenient illustrations of the streaming of protoplasm. 
The granules of protoplasm move in opposite streams side by side, 
turning at the lower end of the tube and inside the grain. The rate of 
motion may be calculated at 1 mm. in 1J-2 minutes. The pollen-tube 
itself was observed to grow at an average rate of 0 * 1 mm. per hour. 
Cell-Membrane.f — Prof. J. Reynolds Green reviews the present 
state of our knowledge of the constitution and chemical properties of 
the cell-wall. It may be stated as certain that the cell-wall is originally 
far from homogeneous ; and that, while cellulose enters very prominently 
into its composition, there are present in it a number of other substances 
which have hitherto been somewhat loosely described under the names 
of pectose, pectine, and compounds of pectic acid. The modifications of 
cell-wall which give rise to gums and mucilages, all of which are pro- 
bably very complex, may well be derived from these, and not from the 
cellulose constituents. These compounds may be arranged in two series, 
neutral and feebly acid. Of the former the most important are pectose 
and pectine ; of the latter, pectic and metapectic acids. There is a 
marked difference between cellulose and pectic substances in their be- 
haviour towards staining reagents. Cellulose acts as a feeble base, and 
takes up acid stains, especially those which contain nitrogen. Pectic 
compounds, on the other hand, act as acids, and require basic stains. 
Haamatoxylin, methylene-blue, vesuvian-brown, and quinolin-blue, stain 
the pectic constituents of the wall, not the cellulose. 
Inclusions in the Living Cell-Wall. J — Herr C. Muller finds, in the 
walls of certain cells in the root of Spiraea Filipendula , crystal-like 
masses, which give none of the reactions of calcium oxalate or calcium 
carbonate, but, on the contrary, those of cellulose. He concludes that 
these crystalline masses are cellulose, and believes their occurrence to be 
very general. 
(2) Other Cell-contents (including Secretions). 
Red Pigment of Flowering-Plants. § — Mr. F. W. Keeble gives a 
resume of the observations and theories of various writers on the red 
pigments of the floral organs known under the general term anthocyan, 
and of their functions. He dismisses, as unsupported by sufficient evi- 
dence, the theory that the red pigment acts as a screen to the chlorophyll, 
preventing its destruction by the action of the sun. On the other hand, 
lie strongly supports Stahl’s view, that its main function is the absorp- 
tion of heat. Hence its very frequent presence in the perianth, anthers, 
or styles of anemophilous trees and shrubs, as in the poplar, hazel, 
Itumex, and Poterium . In the case of the red stigmas of the hazel, it 
may materially accelerate the growth of the pollen-tube towards the 
ovary. 
Structure of Starch-Grains. || — Herr W. Rothert criticises in several 
points Meyer’s views as to the structure of starch-grains, and the nature 
* Nature, lvi. (1897) p. 248. t Science Progress, i. (1897) pp. 344-64. 
X Ber. Deutscli. Pharm. Gesell., 1897, p. 11. See Bot. Gazette, xxiii. (1897) p. 388. 
§ Science Progress, i. (1897) pp. 406-23. Cf. this Journal, 1896, p. 543. 
|| Ber. Deutsch. Bot. Gesell., xv. (1897) pp. 231-9. Cf. this Journal, 1896, p. 80. 
1897 2 f 
