ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
711 
Herr R. Meissner * * * § corroborates Stahl’s results in the main. He 
finds that when dorsiventral leaves are inverted their power of assimi- 
lation is reduced ; while the assimilation of isolateral leaves is only 
slightly affected by inversion. 
Nutrition of Green Parasites.! — M. G. Bonnier points out that 
parasitic flowering plants which contain chlorophyll present all inter- 
mediate stages between those which derive their carbon almost entirely 
from their host, and those which obtain it mainly from their own power 
of assimilation. Thus Euphrasia officinalis gives out no oxygen, even in 
a bright light, and Bartsia alpina and Bhinanthus crista-galli only a very 
small quantity ; while Thesium liumifusum , T. pratense , and Pedicularis 
sylvatica, although they have well-developed haustoria, exhibit a notable 
degree of assimilation, which is still more pronounced in Melampyrum 
pratense , sylvaticum , and nemorosum. The former, therefore, notwith- 
standing their green leaves, are true parasites; while the latter, not- 
withstanding their well-developed haustoria, display but a feeble 
parasitism. 
Influence of Mechanical Resistance on the Development of 
Cells.j; — After reviewing the conclusions of Pfeffer and others, § Mr. 
F. C. Newcombe describes experiments of his own on this subject, from 
which he derives the following results : — The meristematic tissue of 
growing points, intercalary zones, and cambium will preserve its func- 
tional capability for a considerable period when growth is prevented 
by an external mechanical resistance. Under such circumstances the 
tissue remains apparently unaltered, the cells do not divide, and neither 
the thickness nor the composition of the cell- wall undergoes any change* 
External resistance delays all the processes of development, such as the 
differentiation of tissues, lignification of the elements of the vascular 
bundles, formation of cork, &c. Cells which reach their permanent 
development in these conditions have a smaller size and thinner walls 
than is normally the case. The power of cambium to form new cells 
under external pressure is greater than that of tissues derived from the 
cambium. 
Exchange of Carbon Dioxide and Oxygen. || — In a fresh series of 
experiments on a variety of flowering plants, M. T. Schloesing finds the 
CO 
proportion -—-2 to be very nearly identical, viz. 0-848-0*90. With 
O2 
Algae ( Protococcus vulgaris, Chlorococcum infusionum, Ulothrix suhtilis , 
Scenedesmus quadricauda ), the proportion was somewhat smaller, about 
0-74. 
Amount of Water absorbed by Roots.! — In the case of Musanga 
Smithii, a tree 20-25 m. high, belonging to the Urticaceae, growing in 
French Congo, M. H. Lecomte was able to measure the amount of water 
* ‘ Beitr. z. Kenntn. d. Assimilations-Thatigkeit d. Blatter,’ Bonn. See Bot. Ztg,, 
lii. (1894), 2 te Abtheil., p. 250. 
t Bull. Sci. France et Belg., 1893. See Bonnier’s Rev. Gen. de Bot., vi. (1894) 
p. 310. i Bot. Gazette, xix. (1894) pp. 149-57, 191-9, 229-36. 
§ Cf. this Journal, ante, p. 590. 
|| Comptes Rendus, cxvii. (1893) pp. 756-9, 813-6. Cf. this Journal, 1893, p. 214. 
! Op. cit., cxix. (1894) pp. 181-2. 
3 c 2 
