70 BULLETIN 9-57, U. S. DEPAETMENT OF AGRICULTURE. 



(2) Seventy-eight black currant bushes, badly rusted in 1914 were wintered in 

 the nursery rows, and transplanted April 12, in various gardens, isolated as far as 

 possible from infected white pines and currants. These were inspected six times 

 dmlng the summer, the last inspection being made on October 2. At this date all 

 were still free from rust except two bushes, on each of which a few rusted leaves 

 were found. ■ There is reason, however, to suspect that these infections might have 

 been due to spores carried from currants about a mile distant from the garden in 

 which they occurred. In no case was rust found on any of these currants which 

 were located more than a mile from a source of infection. 



(3) A number of bushes from the same source as No. 2 were planted in five lots in 

 a region known from personal observation to have been entirely free from the rust in 

 1914, and which is 60 miles from the nearest known source of infection. Of the 100 

 bushes set out here only one developed rust, and this late in the season. All con- 

 ceivable sources for this infection have been accounted for except two, viz, the 

 wintering over of the rust on the currant itself, or accidental infection from spores 

 earned on the writer's clothing while making an inspection on May 24. 



In 1917, V. B. Stewart (152) tested the possible overwintering of 

 the fungus by means of spores adhering to diseased bushes of Rihes 

 nigrum. These were heavily infected in 1915 and 1916. In August, 

 1916, they were defohated, and 200 were dug and placed in a storage 

 cellar in October, where they remained all winter. In 1917, they 

 were sent to Ithaca, N. Y., and set out in a field. The disease had 

 not been known within 40 miles. The disease did not appear upon 

 them up to October 9, 1917. 



The possibihty of overwintering in Ribes buds was brought to the 

 writer's attention by infections of petioles (131, 134, 135), by which 

 means it seemed entirely possible for the mycelium to travel from a 

 leaf blade down the petiole and thence into the stem and bud in the 

 axil of the leaf. While many diseased petioles have been examined, 

 no indication of the migration of the hyph^ into the stem or bud has 

 yet been seen. Direct examination of buds on heavily infected 

 bushes has also failed to yield any indication of bud-scale infection 

 (151). McCubbin (85) suggested but could not prove that infection 

 of partially opened buds late in the fall might result in some of the 

 infected leaflets surviving the winter and developing the disease the 

 next spring. York ^^ successfully inoculated the inner bud scales of 

 opening buds of Rihes nigrum with seciospores, suggesting overwinter- 

 ing in this way. 



The possibility of green leaves living over winter on Ribes plants 

 out of dc "trs has been investigated. In three cases, the writer had 

 Ribes plants growing in pots plunged in sand out of doors at Wash- 

 ington, D. C, retain green leaves through the winter until the spring 

 weather of March, 1918, set in. One plant of Cumberland goose- 

 berry and two plants of Utah Yellow currants did this. They were 

 taken as specimens on March 22, when warmer weather set in. The 



51 York, H. H. Op. cit. 



