NOTES AND ABSTRACTS. 
503 
infected by them. At the same time it is probable that injured portions of tomato 
foliage might be readily inoculated by spores from the potato. — F. J. C. 
Plasmopara viticola, Studies on. By C. T. Gregory (Rep. Inter. Congress 
of Viticulture, California, 1915). — This is a careful and full study of the fungus 
which causes the " downy mildew " of the vine, which should be consulted by all 
interested. Three points in particular merit reference. The spores germinate 
best at about 50 0 F., not at all at a high temperature. No hibernating mycelium 
has been found, and the author considers oospores are the principal, and probably 
the only, method by which the disease is carried over from one year to another. 
Some varieties of vine are less susceptible than others, but the degree of suscepti- 
bility does not appear to be connected with morphological differences, but rather 
with some physiological difference hitherto undiscovered, — F. J. C. 
Pollen-grains of Apple and other Fruit Trees, On the Germination of the. 
By T. Adams (Bot. Gaz. lxi. p. 131). — 'After enumerating several reasons why 
an individual flower may fail to produce fruit, the author describes his observa- 
tions on the germination of the pollen-grain in a cane-sugar solution. He en- 
deavourfeto answer the questions (1) What strength of sugar solution gives the 
most rapid germination ? (2) How is the germination of pollen-grains affected by 
temperature ? (3) What is the rate of growth of the pollen-tube ? (4) How long, 
under the most favourable conditions, do the pollen-grains retain their vitality ? 
The following are some of the general conclusions arrived at : 
The strengths of the sugar medium were best for : — Apple 2*5-10 per cent., 
pear 4-8 per cent., strawberry 8 per cent., loganberry 4 per cent., raspberry 
and black currant 16 per cent. 
Some pollen-grains of apple germinated in twelve hours ; temperature, 
3-5° and 7 0 C. Some varieties of the same species appeared to have more 
vigorous pollen-grains than others. 
Of the temperatures employed, 2o°-23° C. gave the quickest germination. 
A few pollen-grains of apple formed short pollen-tubes after being kept dry 
for three months, of pear after ten weeks, black currant, ten weeks, but all others 
were dead after two months. — G. H . 
Pollination. By J. B. Dental (Rev. Hort. Aug. 16, 1916). — An interesting 
article on the principles of fertilization of plants and nature's devices in that 
connexion. — C. T. D. 
Pollination of Pomaceous Fruits : Bud Formation. By F. C. Bradford 
(U.S.A. Exp. Stn., Oregon, Bull. 129; May 1915 ; figs.). — It is shown that in 
the case of the apple the differentiation of the flower bud begins in early July 
and continues until a resting stage is reached about the end of November. Later 
developments occur somewhat rapidly in February and March and appear to 
be more dependent upon external influences than are the early changes. Climate, 
it is said, has little effect on the rate of the first changes. — F. J. C. 
Pomaceous Fruits, Black-rot, Leaf-spot, and Canker of. By L. R. Hesler 
(U.S.A. Exp. Stn., Cornell, Bull. 379, Aug. 1916). — This bulletin gives a very 
full account of black-rot, leaf-spot, and canker of pomaceous fruits, which is 
primarily a disease of the apple, although other hosts recorded include the pear, 
quince, and crab. " Black-rot " is the name applied to the disease in fruit, while 
the term " leaf -spot " is given to foliage lesions. " Canker " is an unqualified 
term commonly applied to the disease when it occurs on the bark. The history 
of each form of the disease is dealt with in detail, and the geographical occurrence 
of the fungus, which appears to be very generally distributed throughout the 
temperate regions, is also considered. The loss annually arising from the disease 
is difficult to estimate, more especially because the canker form is often confused 
with other cankers, and difficulty thus arises in obtaining reliable information. 
Much damage occurs to fruits in storage, and when attacked they are rendered 
worthless so far as their market value is concerned, The damage to foliage 
depends on the extent of the infection, and in severe cases the tree may be de- 
foliated from six to eight weeks before the ripening of the crop. It is reported 
that the canker stage is responsible for much injury to branches, while young 
nursery stocks also suffer. The writer deals with the symptoms of the disease 
on the fruit, leaves, and branches, and records the pathogene to be the fungus 
Physalospora Cydoniae Arnaud, the morphology of which is admirably treated. 
Isolation and inoculation experiments receive full attention. 
The methods of control for black-rot are (1) spraying with a 0-03 per cent, 
solution of copper sulphate or Burgundy mixture, the first application taking 
