60 BULLETIN 957, TJ. S. DEPARTMENT OF AGRICULTURE. 
Germination of fresh, urediniospores usually takes place readily in 
tap water. Gravatt found that distilled water gave poorer germina- 
tion than tap water. Colley (20) found that the germ tube pushes 
through the exospore without the aid of a germ pore. ' The contents 
of the spore soon pass into the young germ tube, which may extend 
some distance over the surface of a Ribes leaf. Entry to the interior 
of the leaf appears to be through the stomata. The urediniospores 
germinate in about five and one-half hours (28) in drops of distilled 
water on glass slides. 
During germination studies in 1918, York 38 occasionally found 
germinating urediniospores which formed secondary conidia. An in- 
vestigation of the conditions causing their formation showed that 
newly formed urediniospores usually do not produce the secondary 
conidia in tap water, while old urediniospores were more likely to 
produce them. The following species produced them, the frequency 
increasing in the order named: Ribes lacustre, R. cynosbati, R. vulgare, 
R. reclinatum, and R. nigrum. Urediniospores from R. glandulosum 
did not produce secondary conidia. Urediniospores exposed in bags 
of mosquito netting out of doors gave especially abundant secondary 
conidia. Urediniospores from R. nigrum produced secondary conidia 
in weak solutions of ammonia, maltose, tannic acid, gallic acid, malt 
extract plus gallic acid, lactose plus tannic acid, and lactose plus 
gallic acid. They were especially abundant in the last solution. 
They were not produced in pine decoction, weak solutions of ether, 
lactose, maltose plus tannic acid, and maltose plus gallic acid. A 
limited number were produced in water. They form on the ends of 
the germ tubes or laterally and are capable of producing a germ tube 
themselves. Similar secondary conidia have been noted by Tulasne 
(175) in cultures of Cronartium asclepiadeum, and they have been 
noted by Plowright (109) and Sappin-Trouffy (122) in other Uredi- 
nales. 
LONGEVITY OF THE UREDIXIOSPORES. 
The first experiments in testing the longevity of urediniospores of 
Cronartium ribicola seem to have been carried out by McCubbin 39 in 
1916. His manuscript account of these experiments follows: 
The spores used for this series were all collected on the same day. They were dried 
on paper for a few hours and then placed in a number of small bottles plugged lightly 
with cotton, the contents of each bottle being available for a single inoculation. 
Half of these bottles were kept on a shelf in the laboratory, where they were dry and 
exposed to weak light, and the other half were placed under a bell jar on the soil 
in a garden, exposed to changes of humidity, temperature, and light. 
At stated intervals a bottle was taken from each set and the spores within were 
shaken up with a small amount of distilled water. By the use of a small atomizer 
the suspension of spores was then sprayed on the under side of the leaves of small 
38 York, H. H. Op. cit. 
39 McCubbin has very kindly allowed the use of his unpublished data so as to make this account as com- 
plete as possible. 
