710 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
tlie author explains this on the hypothesis that Pedicularis reached that 
country and became adapted to self-pollination before the arrival of the 
insect. Saxifraga oppositifolia is abundantly visited by the bees, and 
Matthiola nudicaulis to a smaller extent. Polemonium pulchellum is not 
visited by them. 
In Impatiens fulva Mr. T. Meehan * states that the perfect flowers 
are, equally with the cleistogamous ones, self-fertile, insects taking no 
part in the pollination. Nectar is present in the spurs both of the 
cleistogamous and of the perfect flowers. 
Pollination of the Hop.j — In a detailed account of the anatomy of 
the hop-plant, Dr. J. Behrens describes the geotropic and heliotropic 
curvatures of the female inflorescence, by which it becomes specially 
adapted for anemophilous pollination. 
Pollination of the Pear.J — The results of a large series of experi- 
ments made by Mr. M. B. Waite on a great number of varieties of the 
pear in the United States are decidedly favourable to crossing. He 
states that many of the common varieties are partially or wholly inca- 
pable of setting fruit when limited to their own pollen, while some other 
varieties are capable of self-fertilization. Pollen from another tree of 
the same variety acts no better than pollen from the same tree. The 
state of nutrition of the tree and its general environment atfect its ability 
to set fruit, either with its own pollen or with that of another tree. If 
self-fecundated pears contain seeds, they are usually abortive. Even 
with those varieties which are capable of self-fecundation, the pollen of 
another variety is pre-potent. 
(2) Nutrition and Growth, (including- Germination, and^Movements of 
Fluids). 
Transpiration and Assimilation. — Prof. E. Stahl § has undertaken 
a series of experiments to determine the connection between these pro- 
cesses in living plants. He distinguishes between stomatal and cuticular 
respiration, the latter being comparatively insignificant with land plants 
so long as they have a sufficient supply of water. In many plants it is 
certain that the stomates give off water directly into the air, and not 
through the adjacent epidermal cells. Since the stomates open most 
widely when the air is saturated with moisture, and when they are at 
the same time exposed to the action of the sun, a large amount of water 
in the air may promote transpiration. In many plants which grow in 
moist situations, the stomates do not close. But, as a general rule, when 
a leaf withers, the stomates close, and the leaf loses its power of forming 
starch. Assimilation takes place most rapidly when there is direct 
sunshine, and when the air is at the same time moist, i. e. when the 
stomates are fully open. The essential part played by the stomates in 
assimilation can be proved by artificially closing them by some gummy 
substance which does not injure the plant, when the process of assimila- 
tion is almost entirely suspended. 
* Proc. Acad. Nat. Sci. Philadelphia, 1894, pp. 54-7. 
t Flora, lxxviii. (1894) pp. 361-98. 
X U.S. Deptmt. of Agriculture ; Div. of Veg. Pathology, Bull. No. 5, 86 pp. r 
12 pla. and 4 liga., 1894. § Bot. Ztg., lii. (1894) l te Abtheil., pp. 117-45 (1 pi.). 
