180 American Gooseherrif-M ildeiv 



It is possible, but I think very unlikely, that in these cases where an 

 examination in the spring showed only perithecia with dead asci that 

 all the mature (living) perithecia had fallen previously to the ground. 

 It seems far more probable that this material had never reached that 

 stage of development at which the perithecia can remain alive through 

 the winter. If so, the reason for this failure to mature may be due to 

 the influence of new factors which the mildew encounters in this country 

 — such as the " constitutional " characters of European varieties of 

 gooseberries, or to the weather conditions obtaining in this country in 

 the late summer or autumn. It may possibly prove to be the case that 

 it is only the perithecial stage which is formed early in the season, 

 reaching maturity about July or August, that is really dangerous, and 

 that later-developed perithecia do not survive the winter. 



It would of course be unwise to generalise from observations made 

 so far on material obtained in one season only ; but there seems clear 

 evidence that both the fruit-grower and the official administrators of 

 the American Gooseberry-mildew Orders have a new fact to reckon with, 

 viz. the natural death, before the spring, of some amount of the peri- 

 thecial stage of the American gooseberry-mildew. 



Postscript. Since the above was written, I have had the opportunity 

 of examining further " over wintered " material of S. mors-iivae collected 

 at the end of April and during May. 



The first lot of material collected at the end of April, was kindly 

 obtained for me by Mr Gibson (Inspector for American Gooseberry- 

 mildew for Surrey) from Farnham, Newdigate, and Witley. Thirty- 

 four shoots bearing patches of the perithecial stage were sent ; these were 

 all closely examined. Twenty-two shoots bore patches of deep-brown 

 persistent mycelium, which on examination proved to be either quite 

 barren with no perithecia, or with just a few (dead) perithecia. The 

 appearance of the barren patches suggested that no perithecia had 

 ever been formed {i.e. that the development of the winter stage had 

 been stopped), and not that the perithecia had fallen out from them, 

 since the densely interwoven mycelial patches showed — in many cases 

 at all events — no signs of having been worn thin or disintegrated under 

 the action of weather conditions ; in a few cases the mycelial patches 

 may have been partly worn away as the result of " weathering." On 

 more than 50 per cent, of these diseased shoots there was a completely 

 barren, although dark brown, mycelium. 



In the remaining twelve examples perithecia had been produced 

 abundantly on the shoots, but in no case was a living ascus found inside 



