Some Observations on the Life-history of 
Nectria galligena, Bres. 
BY 
DOROTHY M. CAYLEY, 
Research Student, John Innes Horticultural Institution , Merton , Surrey. 
With Plates IV and V. 
Introduction. 
T HE present investigation was started with the object of finding, if 
possible, the most vulnerable stage in the life-history of N. galligena at 
which fungicides could best be applied to prevent the spread of the disease. 
This involved a complete study of the life-history of the fungus itself, and 
more especially the transition from the summer or conidial stage to the 
resting or perithecial stage. During the course of this part of the investi- 
gation a few hitherto unrecorded observations were made, which were 
thought to be of sufficient interest to allow of publication. 
The description of the life-history is necessarily incomplete, owing to 
technical difficulties. The fungus is very small and difficult to deal with. 
The fruiting stages occur on dead or dying bark, and it was found impossible 
to fix and cut serial microtome sections thin enough to allow of accurate 
microscopical investigation. It was only after a medium had been elaborated, 
on which the fungus would complete all the known stages in its life-history 
in pure culture, that further progress could be made. The preparations on 
bark, however, served as controls for comparison with the growth in pure 
culture on artificial media, and the development of the life-cycle proved to 
be very much the same in both cases. 
The fungus is a common parasite on apple and pear trees, giving rise 
to one of several forms of canker which occur on the stems and branches. 
Nectria , under the name of N. ditissima , has been described by various 
workers on a number of other host plants besides apple and pear, such as 
copper beech, oak, hazel, ash, limo^and others ; but it is questionable if 
these different investigators were really dealing with one and the same 
fungus. Nectria on beech was first described by Tulasne (31), in 1865 , 
under the name of N. ditissima , and later Goethe (14-18) was able to show, 
[Annals of Botany, Vol. XXXV. No. CXXXVII. January, 1921.] 
