Nectria galligena , Bres. 
85 
Development on Artificial Media. 
Microspore Stage . 
All stages in the life-history of N. galligena, as described by Hartig 
and Goethe under the name of N. ditissima , were observed to occur in pure 
culture. Ascospores, obtained from tendrils of dehiscing perithecia on 
apple bark, sown on potato + 1 per cent, glycerine, give rise in the course 
of a few days to a weft of fine, spreading, hyaline mycelium. This mycelium 
is sparsely septate, and the branching more or less monopodial. Unicellular 
microspores, 5-7 jjl x i-i*5 ju, are abstricted from the tips of the fine hyphal 
branches, and not from differentiated conidiophores. The function of these 
microspores is not known. 
As the fungus colony grows, coarser thicker-walled mycelium develops 
which is much more septate than the -above. The cell-walls are tinged 
with yellow and the cells contain numerous oil-drops. Branched conidio- 
phores (Fig. 11) arising from a sporodochium of closely interwoven hyphae 
give off enormous numbers of septate macroconidia, the Fusarium Will - 
kommii stage of Weese ( 34 ). In the host plant this stage occurs during 
the months of September and October, or even later if the weather is open 
(Fig. 1). The macroconidia when fully developed are hyaline, slightly curved 
with rounded ends, 5-7 septate, 6 5-75 /x x MS ' 5 (Fig. 10), and each cell is 
uninucleate at first. These macrospores can be easily distinguished from 
the microspores. They are considerably larger, although all stages from 
the unicellular to the multicellular macrospores have been observed both 
on artificial media and on apple barla The first-formed macrospores on 
a young sporodochium as a rule have fewer septae. 
Macrospores grown in a hanging drop germinate mostly from the 
terminal cells at either end of the spore (Fig. 13 b). The middle cells, under 
moist conditions, do not germinate very readily. Cultures made from 
macrospores give rise, in their turn, to microspores and follow the same 
sequence of stages as cultures' made from ascospores. This is the case 
when macrospores drop away front the sporodochium. But under certain 
conditions, when undisturbed, as is mostly the case on artificial media, and 
also in the open in calm autumnal weather, a considerable number of 
macrospores remain in situ and anastomose by throwing out connexions 
from their central and even their terminal cells (Fig. 13). Only one cell 
may link up with another cell of a neighbouring spore, or several cells of 
one spore may be linked with cells of a neighbouring spore or spores. The 
result is the formation of a palisade pseudo-tissue formed by linked macro- 
spores. This linking is of very common occurrence both on bark and 
artificial media. This palisade tissue helps to increase the bulk of the 
sporodochium. At this stage the behaviour of the nuclei of the macrospores 
is interesting but little understood. The passage of the nucleus from the 
