32 BULLETIN 957, U. S. DEPARTMENT OE AGRICULTURE. 
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 seciospores. Open blisters 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 seciospores are produced by an aecium of 
Cronartium ribicola for more than 14 days. Posey and Gravatt 13 
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. 14 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 15 working at North Conway, N. H., in 1918, found that a few 
individual secia contain viable spores for from 20 to about 30 days. A 
study of secial production on single cankers showed that secia 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., 16 
the secial season in 1919 was slightly more than two months in length. 
After the main secial season, late straggling secia form. Rhoads 14 
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 Bibes 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 seciospores may remain viable over winter 
in the secia, since Dosdall (29) has found that seciospores occasionally 
retain viability until the next spring. 
13 Posey, G. B., and Gravatt, G. F. Op. cit. « y or k, H. H. Op. cit. 
u Rhoads, A. S. Op. cit. ^Pennington, L. H. Op. cit. 
