496 SUMMARY OF CURRENT RESEARCHES RELATING TO 
erroneous observations. Even leafless parasites ( Balanophora , Cyfinus, 
Hydnora , Cuscuta , Orobanche , &c.) contain abundance of starch in their 
parenchyme, which must have been formed in the tissues of the parasite. 
The carbon dioxide is formed in such plants, as in animals, by the con- 
sumption of their own carbon, this carbon being derived from the sap of 
the host-plant. But certain secondary products, such as the colouring 
matter of the flowers of Cuscuta and of some species of Orobanche , must 
be formed afresh in the tissues of the parasite. Many leafless parasites 
possess stomates and well-developed spiral vessels. 
Assimilation of Leaves.* * * § — Herr H. Yochting describes an apparatus 
designed to determine the question whether the growth of each leaf is 
due to the energy of the assimilation in that particular leaf. The result 
of a number of experiments enabled the author to answer this question 
in the affirmative, both as regards the mature organ aud the leaf in 
course of development, though this does not apply to the earliest stages 
of the development of leaves or of the leaflets of compound leaves. 
Absorption of Atmospheric Nitrogen by Plants. t — Messrs. W. O. 
Atwater and 0. D. Woods have carried out a long series of experiments 
in growing various plants — chiefly peas, lucerne, oats, and maize — in 
soils saturated with different infusions which promote the formation of 
root-tubercles. They find that, in all cases where tubercles are pro- 
duced, there is a distinct absorption of nitrogen from the atmosphere. 
They assert that atmospheric nitrogen is undoubtedly acquired during 
the growth of peas and lucerne, and that the amount of nitrogen absorbed 
is in proportion to the number of tubercles. The addition of soil- 
infusion is not, however, necessary for the production of the tubercles. 
The cereals do not, as a rule, possess the power of acquiring nitrogen 
from the atmosphere, nor are root-tubercles formed on them as in the case 
of leguminous plants. 
Perforation of Potatoes by the Rhizome of Grasses.! — M. A. Prunet 
has investigated the perforation of the tuber of the potato by the rhizome 
of certain grasses, especially Cynodon Dactylon and Triticum rejpens, 
which is not an uncommon occurrence. He finds that it is not of advan- 
tage to the perforating organ in the way of obtaining nutriment from the 
reserve-materials in the tuber. In immediate contact with the per- 
forating rhizome is a layer of disintegrated tissue of the tuber, and next 
to this a suberous sheath which completely cuts off the rhizome from the 
nutritive tissues of the tuber. The terminal bud of the rhizome presents 
no appearance of producing any substance of a diastatic nature, and the 
small roots which proceed from the rhizome are entirely destitute of 
root-hairs. 
(3) Irritability. 
Compass-plants.§ — In addition to the well-known instances of 
Silphium laciniatum, species of Laduca, &c., the leaves of which present 
their two surfaces successively to different points of the compass in 
order to prevent excessive radiation, Prof. G. Arcangeli describes 
* Bot. Ztg., xlix. (1891) pp. 113-25, 129-43 (1 pi.). 
f Amer. Chem. Journ., xii. (1890) pp. 526-47; xiii. (1891) pp. 42-63. 
+ Rev. Gen. de Bot. (Bonnier), iii. (1891) pp. 166-75 (2 figs.). 
§ Nuov. Giom. But. Ital., xxiii. (1891) pp. 145 -9. 
