254 
start it the next spring, although they have been found on garden 
lettuce by Vize* in England, and may occasionally occur on it else- 
where. 
ROTTING OF CHERRIES AND PLUMS. 
Oidium fructigenum S. & K. 
Von Thiimen in his work on the fungi of fruitst says that un- 
doubtedly this fungus is to be considered the most widely distributed 
and perhaps the most noxious and destructive of all kinds that oc- 
cur upon fruit; a statement especially applicable in this country in 
relation to cherries, plums and other stone fruits. The loss of plums 
and cherries from rot before they are gathered from the tree is very 
large, detracting heavily from the profits of their cultivation; this 
rotting is almost solely due to the attack of this single species, Even 
after harvesting the rot caused by the growth of the spores of this 
fungus, which are adhering to the fruit when gathered, adds greatly 
to the loss of a naturally perishable crop. 
The fungus consists of colorless, much branched and septated 
threads permeating the tissue of the fruit and causing it to turn 
brown and decay, the surface of the fruit changing to brown, more 
often a light brown, at the same time. When the fungus produces 
spores, which does not always take place at once, being largely con- 
trolled by the amount of moisture in the air, the surface of the fruit 
is covered with tufts, more or less distinct and about one sixteenth 
inch high, of dirty-white or gray pulverulent fruiting threads. The ~ 
tufts are somewhat compact, but readily fall into dust when rubbed. 
On apples and similar fruit they are at first distinct and pustular, 
. but soon coalesce and become continuous; on plums and cherries the 
tufts are generally larger and less regular. 
The fruiting threads consist of short sections, each a little 
more swollen as they approach the ends of the threads where 
the sections are elliptical. The sec- 
tions when ripe are separated and 
form the spores. When well grown 
in moist air they are abundantly dich- 
otomous, as shown in fig. 5 (one 
thread is shaded and the other not to 
render them more distinct), a feature 
not well shown in any of the illustra- 
tions Iam familiar with, and Von 
\ Thiimenf has described and figured 
them as unbranched. The branches 
grow at the extremities, giving rise 
to new spores until the full length 
and maturity is attained, then the 
end spores successively drop away. 
| Although this is a common fungus 
Fig. 5—Two fruiting threads of and known almost from the days of 
Oidium fructigenum, before the JT innzeus, it does not seem to have 
spores have begun to fallaway. Mag- : : 
nified 250 diameters. Original. been very carefully studied; Euro- 


*Gardeners’ Chronicle, X XI, p. 418, and illustrated in Smith’s Diseases of Crops, 
p. 275. 
+ Fingi Pomicoli, p. 23. 
BUCK Pie eos; Dir eA GL ok bc 


— A TS TR a = 
a 
