540 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
traction of tlie root ; eitlier tlie contractile primary root perishes at 
an early period, and is replaced by adventitious roots ( Lilium Martagon , 
Fragaria vesca, Crocus verms , &c.), or the primary root persists ( Tarax- 
acum officinale , Gentiana lutea, &c.) ; (3) by the growth of the leaf- 
stalk ( Oxalis rubella). In the majority of cases more than one of these 
forces combine to cause the sinking of the rhizome or bulb to the re- 
quired depth. 
j8. Physiology. 
(1) Reproduction and Embryology. 
Cross-Pollination and Self-Pollination. — Mr. C. Robertson’s* latest 
contributions to this subject consist of a list of the insect visitors and a 
description of the mode of pollination in species of Polygonum, Dirca, 
Euphorbia, Salix, and Iris. All the species of Salix observed by him 
are entomophilous. Similar information is given with regard to species 
belonging to the Monocotyledonous genera Polygonatum, Smilacina, 
Uvularia, Trillium , and Melanthium. 
M. J. Briquet | gives some very interesting details regarding the 
mode of pollination of 20 species, natives of the Western Alps. While 
some are partially or entirely autogamous, he regards none of them as 
truly anemophilous ; the majority are entomophilous. In Helianihemum 
polifolium, in addition to the ordinary hermaphrodite, there are a small 
number of somewhat smaller male flowers, in which the gynoeeeum is 
entirely suppressed. The number of stamens in the hermaphrodite 
flowers varies greatly ; it is always small in the male flowers. 
Herr E. Ule $ gives further particulars respecting the structure and 
mode of pollination of the flowers of Purpurella cleistopetala [nom. 
emend,]. The unopened corolla appears to be a protection against the 
heavy rain which prevails in the district. The pollinating insects are 
small ants which find their way into the corolla. Scarcely any Hymeno- 
ptera were observed in the region. The structure of other species of 
the genus is described, all of which are proterandrous, and of other 
species belonging to allied genera. 
The same author § describes the adaptations for pollination in another 
Brazilian plant, Dipladenia atroviolacea (Apocynacece). The flowers 
are here also nearly completely closed. Pollination appears to be 
effected by humming-birds. 
(2) Nutrition and Growth (including Germination, and Movements 
of Fluids). 
Amount of Light which is most favourable to the Growth of 
Plants.]’! — Prof. J. Wiesner proposes the expression L = 4 for the 
specific light-requirement of any plant, J being the total intensity of the 
light which reaches the plant, the full intensity of daylight being unity. 
* Bot. Gazette, xxi. (1896) pp. 72-81, 266-74. 
t Arch/Sci. Phys. et Nat., i. (1896) pp. 234-62, 332-63 (3 pis.). 
X Ber. Deutsch. Bot. Gesell., xiv. (1896) pp. 169-78 (1 pi.). Of. this Journal, 
ante, p. 328. § Tom. cit., pp. 178-9 (2 figs.). 
II SB. K. Akad. Wiss. Wien, civ. (1895) pp. 605-711 (4 pis.). Of. this Journal, 
1895, p. 334. 
