SCIENTIFIC SUMMARY. 
207 
assert themselves. On this point the further questions arise, whether the 
fungi prevail simply in virtue of the absence of adverse and vigorous com- 
petition, or whether to a greater or less extent as parasites, and so at the 
expense of the sluggish underground growth of the plants in association with 
them ; or, lastly, have these plants the power of assimilating nitrogen in 
some form from the atmosphere, or in some form or condition of distribution 
within the soil not available (at least when in competition) to the plants 
growing in association with them. 
Germination of the Spores of u Hemileia Vastcitrix.” — The germination of 
this curious fungus has not as yet been observed in Europe ; but Dr. G. H. 
K. Thwaites, of Ceylon, has given the results of his experiments on germi- 
nation. He says that it is not difficult to induce germination. Mature 
spores removed from a diseased leaf, and laid upon charcoal, kept constantly 
moist, commence to germinate in a few days. This process consists in the 
spore becoming somewhat enlarged, and its contents converted into one or 
more globose translucent masses. From each of these a filament is deve- 
loped, which grows very rapidly, and becomes more or less branched. At 
the termination of some of these branches secondary spores are produced in 
the form of radiating necklace-shaped strings of little spherical bodies of 
uniform size, and this form closely resembles the fructification of an 
Aspei'gillus. Another observer in Ceylon (Mr. Abbay) has seen another 
form of secondary spores arranged in simple rows of spherical bodies — a 
good deal larger than those radiately arranged, but still exceedingly minute. 
These inconceivably numerous secondary spores may be easily transported 
by the slightest breath of air from place to place, and from plantation to 
plantation. Messrs. Berkeley and Broome have intimated that this fungus 
seems to hold an intermediate place between Uredines and Moulds. The 
germination, as well as structure of the species, is thus seen to be very 
unique and interesting. — u Grevillea,” March 1876. 
11 The Garden ” Botanical Newspaper now issues with each weekly 
number a full-page coloured plate of some interesting specimen of plant. We 
have seen two of the representations, and can speak in the highest terms 
of the efforts of the artist. 
Emissive Power of Leaves. — u Silliman's American Journal ” states that 
M. Maquenne, on comparing the quantity of water evaporated by a cultivated 
soil during vegetation with that furnished by the rain, finds in general an 
excess in favour of the former. May not this excess be caused by the dew 
deposition at night on the plants ? When the dew is measured by a plu- 
viometer the results are much too small. The leaves condense far more 
than surrounding bodies, and their temperature may fall six or eight de- 
grees below the air, showing that their emissive power is much greater 
than that of the metal surfaces of the pluviometer. To determine the emis- 
sive power of leaves, a Leslie cube was employed ; one of its faces was 
blackened, another covered with leaves, and the two surfaces turned suc- 
cessively to the pile. The temperature of the water did not exceed 40°, to 
avoid injuring the leaves. The deflections were measured by a mirror and 
scale, and a twentieth of a degree was easily observed. On trying several 
kinds of leaves it appeared that their emissive power did not differ greatly, 
was the same on both sides, and had an average value of 94, that of lamp- 
