310 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
frequently lias abortive stamens ; Ranunculus Ficaria is generally infer- 
tile ; Petasites vulgaris is nearly always male ; TJlex eurojpseus and 
Primula vulgaris set but little fruit. In other cases the advantage of the 
early flowering is clearly in the flowers opening before the appearance of 
the leaves, which obstruct pollination, whether by wind or by insects. 
Germination of Pollen-Grains.* * * § — Prof. A. Hansgirg contests the 
opinion of Lindforss,! that those plants the pollen- grains of which perish 
in water, have their anthers and their stigmas protected in the flowers 
against the access of rain. He gives two long lists of plants whose 
pollen germinates readily in pure water ; one of these lists being of 
species whose sexual organs are protected against rain, while in those 
of the other list there is no such protection. In a very large number 
of other plants the pollen-grains either do not germinate in water, or 
only with great difficulty. 
(2) Nutrition and Growth, (including: Germination, and 
Movements of Fluids). 
Assimilating Energy of the Blue and Violet Bays of the Spec- 
trum.:]:— As the result of a series of experiments, chiefly on Elodea 
( Anacharis ), Herr F. G. Kohl states the following general conclusions as 
to the part taken by the different rays of the solar spectrum in the 
evolution of oxygen from leaves. The assimilating energy of the red 
rays is about one-half that of undecomposed sunlight. The action of 
the blue rays is but little less than that of the reel. The amount of 
oxygen given off in the green rays is not more than half that in the blue. 
The energy of the yellow rays is less, and that of the violet least of all. 
The author distrusts both the eudiometric method of measuring the 
energy of the process of assimilation, and the bacterium method of 
Engelmann. He prefers the results obtained by counting the bubbles 
of oxygen given off, and describes a process by which the actual volume 
of gas thus eliminated can be determined. 
Beciprocal Influence of Stock and Graft on one another.§ — M. L. 
Daniel records the results of grafting Heliantlms annuus (annual and 
few-flowered) on H. Isetiflorus (perennial and many-flowered) and vice 
versa. He finds a direct reciprocal influence of stock and graft. The 
predominant effect of the stock is on the form of the assimilating tissue 
of the graft ; it is also manifested in the flowering ; the graft exercises 
an influence especially on the mode and duration of the development of 
the stock. In the passage of species of Helianthus to the latent state 
there may possibly be a substitution between lignification and the for- 
mation of tubers. 
Influence of Chemical Beagents and of Light on Germination.il— 
Dr. A. J. J. Vandervelde states that all chemical reagents used (salts of 
potassium, sodium, ammonium, barium, strontium, iron, and copper) have 
a prejudicial influence on the germination of seeds. Nitrates are more 
* Oesterr. Bot. Zeitschr., xlvii. (1897) pp. 48-52. Cf. this Journal, ante, p. 138. 
+ Cf. this Journal, 1896, p. 437. 
i Ber. Deutsch. Bot. Gesell., xv. (1897) pp. 111-24 (3 figs.). 
§ Comptes Rendus, exxiv. (1897) pp. 866-8. 
[|| Bot. Centralbl., Ixix. (1897) pp. 337-42. 
