32 BITLLETIlSr 957, U. S. DEPAETMENT OF AGKICULTUEE. 



far north, has much to do with the time that the secia appear. They 

 begin to push through the bark several weeks before they break open 

 and distribute the ssciospores. Open bhsters have been noted as 

 early as April 5 in eastern Massachusetts, but they were nearly three 

 weeks later in the Adirondacks the same spring. Table V (p. 72) gives 

 specific data so far as they are available for this and related dates. 



Klebahn (68) stated that ^ciospores are produced by an secium of 

 Cronartium ribicola for more than 14 days. Posey and Grgfvatt ^^ 

 ■found that seciospore production took place at Kittery Point, Me., in 

 1917, from April 29 to July 1. 



In the spring of 1918, Rhoads made observations at Kittery Point, 

 Me., to determine how long individual secia produce spores.^* On 

 May 3, he stuck pins, bearing numbered pieces of paper, into 300 

 secia on various trees just as they first broke open. On May 20, the 

 peridia of all but 63 of the secia were entirely gone with most of the 

 spores. On May 29 remnants of but 19 were left and on June 4, 

 none. Therefore, in 1918 the seciospore season was about 4 weeks long 

 at Kittery Point, Me. 



York ^^ working at North Conway, N. H., in 1918, found that a few 

 individual aecia contain viable spores for from 20 to about 30 days. A 

 study of secial production on single cankers showed that ascia matured 

 for a period of about 30 days. These infections were all on relatively 

 small twigs and branches. On larger branches or trunks the period 

 may be longer. Study of the period of secial production in that entire 

 region showed that it was approximately 70 days. At Lewis, N. Y.,^^ 

 the secial season in 1919 was slightly more than two months in length. 

 After the main secial season, late straggling secia form. Rhoads ^* 

 noted that secia occasionally develop on areas of bark which bore 

 secia the preceding year, but which were still alive. 



York noted a newly formed secium of Cronartium ribicola near 

 Littleton, N. H., on July 21, 1918 (179). Several still more remark- 

 able cases were noted by York and Ninman at Amery, Wis., on 

 September 15 and 16, 1919. Such late secia appear to be unknown 

 for any of the other stem Peridermiums except C. occidentale, which 

 has an secial season from June to August. Numerous instances are 

 known where C. ribicola was entirely absent on Ribes in a given 

 locality early in the season, but later was found to be present in greater 

 or less abundance. Some of these infections may originate from 

 such late secia. These late aciospores may remain viable over winter 

 in the secia, since Dosdall (29) has found that seciospores occasionally 

 retain viability until the next spring. 



» Posey, G. B., and Gravatt, G. F. Op. cit. is York, H. H. Op. cit. 



"Rhoads, A. S. Op. cit. le Pennington, L. H. Op. cit. 



