89 
Nectria galligena , Bres . 
autumn, develop slowly throughout the winter months, and dehisce in 
spring. Material gathered in February showed perithecia In all stages of 
development ; in April the perithecia are mostly fully grown and about 
to dehisce. 
Pycnidia. 
With regard to the vexed question as to the occurrence of pycnidia 
in the life-history of N . galligena , pycnidia have been seen from time to 
time In preparations of the fungus growing on bark. They occur as a rule 
in close proximity to the perithecia, and appear to originate from the same 
sporodochium (Fig. 16). So far, no mature pycnidia containing spores have 
been observed in any of the pure cultures oh artificial media. On bark, the 
pycnidial wall consists of one or two fairly regular layers of thick-walled 
cells (Fig. 17), whereas the young perithecial wall contains more than two 
outer layers, is much more irregular, and the transition from the outer 
layers to the thin-walled central cells is more gradual than is the case in 
the young pycnidium. Also the internal tissues of the young perithecium 
vary considerably in size of cell and capacity for taking up stains, as 
compared with the central portions of the pycnidium, which stain much 
more uniformly. ' It is, however, somewhat difficult to distinguish between 
pycnidia and immature perithecia, more especially when the latter are filled 
with paraphyses and the sections happen ‘to be transverse or oblique. On 
artificial media, owing to the more irregular growth of the tissues of the 
sporodochium, and the variability in thickness of the walls of young 
perithecia, immature pycnidia may possibly have been overlooked. One 
or two doubtful cases occurred, but it was impossible to arrive at any 
definite conclusion. If pycnidia do occur in the life-history of Nectria 
galligena , of which there is not sufficient proof, they are probably abortive, 
as the fungus will complete its life-cycle from ascospore to ascospore on 
artificial media without the development of pycnidia. The unicellular 
pycnospores (Fig. 17) are abstricted from simple unbranched sporophores in 
acropetal succession. 
Two-celled Multinucleate Spores. 
At the stage in which the young perithecia begin to develop, two- 
celled multinucleate spores (Fig. 8) have been observed both on bark and 
artificial media. Eight or more nuclei occur in each cell, when the spore 
is mature. Unstained, they cannot be distinguished from two-celled 
macrospores, and no signs of germination could be seen in stained 
preparations. 
Summary. 
The fungus described in this paper was isolated from canker on apple, 
and agrees in morphological and biological characteristics with N. galligena, 
