ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
559 
result of experiments dependent on tbo use of congo-red as a staining 
reagent — that the cellulose-membrane is formed out of the outermost 
layer of protoplasm on the surface of the protoplast, in the form of a 
loose pellicle, which, remaining in contact with the protoplasm, grows 
in surface and becomes thicker and denser. The granular protoplasm, 
the parietal layer, and the cellulose membrane, form a connected whole 
with no sharp line of demarcation between them. The author supports 
Pfeffer’s view that the formation of cellulose is directly connected with 
the process of respiration and the breaking up of proteids. 
The nucleus takes no direct part in the growth of the cell-wall, 
although it is usually found in proximity to the growing wall, near the 
apex of the root-hair or rhizoid. In the epidermal cell from which the 
hair springs, the nucleus lias usually a roundish form, and is situated 
near the spot where the hair originates. After a time it passes into the 
hair and gradually assumes a fusiform shape. 
(3) Irritability. 
Nyctitropic Movements.* — Herr L. Jost supplements his previous 
observations on nyctitropic movements in plants with the following : — 
The movements of the perianth-leaves of the tulip and dandelion depend 
on changes in the temperature, and not, to any appreciable extent, on 
changes in the light. The closing of the flowers is not, however, caused 
by an increase of temperature, but by the maintenance, for a consider- 
able time, of the same high temperature which brings about the open- 
ing of the flower. The opening of the flower is caused by a rapid 
growth of the inner surface of the perianth-leaves; its closing by the 
cessation of this, and the more rapid growth of the outer surface. The 
phenomena are the same in the crocus. 
The author differs somewhat from Pfeffer f in his theoretical expla- 
nation of the phenomena of nyctitropic movements. He thinks it more 
probable that in these movements, and in those of nutation, the two 
antagonistic halves of an organ react differently, that the concave side 
exhibits an active retardation of growth or contraction, while the con- 
vex side displays an acceleration of growth or expansion. The move- 
ment of reflexion must, he thinks, be attributed to interior causes. 
With regard to the influence of changes in temperature on the move- 
ments of foliage-leaves ( Pliaseolus , Acacia, Desmodium , Bobinia, Mimosa), 
he states the general rule that in the dark a slow elevation of temperature 
causes opening, a quick elevation closing of the leaflets ; slow depression 
of temperature induces a closing of the leaflet, rapid depression a moro 
rapid closing. 
Nutation of the Sunflower.:]: — Mr. J. H. Schaffner has studied the 
phenomena connected with the diurnal nutation of the flower-heads of 
Helianthus animus (in Kansas). From shortly after sunrise, when tho 
plant is nutating about 60° E., until sunset, there is a gradual movement 
westward until the terminal bud faces W., and the upper part of the stem 
* Jalirb. f. wies. Bot. (Pfeffer u. Strasburger), xxxi. (1898) pp. 345-90(2 figs.). Cf. 
this Journal, 1897, p. 312. t Cf. this Journal, 1894, p. 370. 
j; Bot. Gazette, xxv. (1898) pp. 395-403 (1 fig.). 
