\]. S. Salmon 170 



hitol}' observed, liowever, show the necessity for close investigations to 

 be made to ascertain to what extent the perithecial stage wliich is 

 formed at different times during any one season remains living through 

 the following winter and is the cause of the first spring outbreaks. The 

 facts lately observed would seem to show that there is a real danger — 

 if the American Gooseberry-mildew Orders are carried out by officials 

 without the guidance of a mycologist — of fruit-growers being prosecuted 

 and fined for not removing from gooseberry bushes Ihe mildew in a dead 

 condition. 



In August last year, and during the present spring, I have observed 

 the various details connected with the dehiscence of tlie ripe perithecium 

 and the discharge of the ascospores — a process which I have not before 

 succeeded in observing and one which, I believe, has escaped other 

 investigators. The details will be described in the next number of the 

 Journal of Agricultural Science (now in the press^). The dehiscence of 

 the ripe perithecium was observed to take place in material collected last 

 August, a few^ hours after the perithecia had been supplied with moisture ; 

 similar material collected in November last and kept dry in the laboratory 

 through the winter, proved when examined in February, March, and 

 April, to be alive, the perithecia dehiscing when supplied with moisture. 

 The dehiscence, which occurred either almost at once — the shortest time 

 being 1| hours — or after an " incubation " period of several days 

 — took place at temperatures from about 5° C. to 27° C. 



This living material w^as useful in affording a comparison with 

 examples of the perithecial stage obtained from bushes in the open in 

 the spring, i.e. after it had " wintered." In all cases, so far, such " over 

 wintered" material, which has been obtained from N., Mid., and E. Kent^, 

 proved in February or later, to be dead. In such material the perithe- 

 cium on being pressed open usually exudes drops of an oily nature ; 

 the ascus is not turgid, and is often more or less crumpled ; the asco- 

 spores are filled with some oily material, staining pink with alkannin. 

 No development can be induced on " incubation " at those temperatures 

 which cause living perithecia to dehisce and discharge their spores, 

 and it is clear that such perithecia are dead. 



It seems clear, therefore, that some amount of the perithecial stage 

 of the American gooseberry-mildew which is produced in this country 

 either does not reach maturity or does not survive the winter. 



1 Salmon, E. S. Observations on the Perithecial Stage of the American Gooseberry- 

 mildew {Journ. Agric. Set., vi, p. 187, May, 1914). 



2 Most of this material was kindly sent to me by Mr F. G. Cousins, Inspector for 

 American gooseberry-mildew for Kent. 



