656 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
parachute- like crest of hairs formed from the cells of the outer layer 
of the testa of the seed ; or there may be two such tufts, one attached 
to the seed itself, the other to the funicle. In Catopsis the appendage 
consists of a dense tuft of thick club-shaped hairs, and the inner layer of 
the testa projects above the outer layer. 
Propagation of Opuntia.* — According to Mr. J. W. Tourney, several 
species of Ojpuntia natives of Arizona, belonging to the subgenera Plato- 
puntia and Cylindropuntia, have almost entirely lost their power of sexual 
reproduction ; either they do not produce seeds, or the seeds which they 
produce do not germinate. These species are propagated almost entirely 
by the detachment of joints or branches, which, from the large amount 
of moisture which they contain, retain their vitality, and root in the 
soil, even after the lapse of a very considerable time. The carriage to 
a distance is greatly promoted by their abundant spines and bristles. 
Parasitism of Cuscuta.| — Prof. A. Silvestri records the remarkable 
occurrence of an example of Cuscuta epithymum parasitic on Nicotiana 
tabacum. 
Influence of Lime on Vegetation.^ — An explanation of the fact that 
alpine species of plants are frequently found on calcareous rocks at a low 
elevation and in southern latitudes, is proposed by Dr. S. Nicotra in the 
fact that lime is a bad conductor of heat. 
Influence of Phosphates on the Growth of Plants.§ — According to 
experiments carried on by Herr F. Noll, phosphorus is not indispensable 
to the growth of plants in their earliest stages ; but there comes a time 
when growth entirely ceases if the quantity of this substance which has 
been consumed is not replaced by a fresh supply. The activity of the 
protoplasm in the meristematic cells of the growing point is dependent 
on the presence of phosphorus. But the presence of too large an amount 
of phosphorus may be injurious to the plant. 
Torsion of Pine-trees. |] — As the result of a number of observations 
Prof. R. Hartig states that all pine-trees ( Pinus excelsa') turn to the left 
during the first years of their growth. At a later period (varying from 
the 20th to the 100th annual ring) either the growth becomes straight, 
or a torsion to the right takes the place of the left-handed torsion. This 
twisting is in each case dependent on the oblique direction of the cells 
in the initial cambium layer. No connection can, however, be established 
between this torsion and the length of the cells of the wood-fibres ; this 
latter is regulated by the nutrition of the tree. 
Assimilation of Nitrogen by the Papilionacese.^ — From the results 
of a series of experiments on Vida, Pisum, and Lupinus, and of control- 
experiments on Polygonum Fagopyrum , Herr J. Billwiller supports 
Frank’s conclusions as to the power of certain Papilionacese to assimi- 
* Bot. Gazette, xx. (1895) pp. 356-61. 
f Atti Accad. Pontif. Nuovi Lincei, xlviii. (1895) pp. 37-9. 
t Malpighia, ix. (1895) pp. 220-35. 
§ ‘Der Einfluss d. Phosphaternahrung auf d. Wachsthum u. d. Organbildung d. 
Pflanzen,’ Bonn, 1895. See Bot. Centralbl., lxiii. (1895) p. 184. 
|| SB. K. Bayer. Akad. Wiss. Miinchen, 1895, pp. 199-217 (2 figs.). 
^| * Ueb. Stickstoff-assimilation einiger Papilionaceen,’ Bern, 1895, 50 pp. See 
Bot. Centralbl., lxiii. (1895) p. 152. Cf. this Journal, ante , p. 198. 
