The British Association at Birmingham. 351 
in the various species, and pointed out that the structure of the cell- 
wall varied in the different species. The wall becomes disarticulated 
into H-pieces only in a few species. The zoogonidia are always 
biciliated, and their escape takes place either by disarticulation of 
the filament or by the rapid conversion of the cell-wall into 
mucilage ; after a brief swarming they germinate at once and grow 
into new filaments. The formation of aplanospores was described, 
and also the germination of the latter. The systematic position of 
the genus Microspora , was discussed and it was suggested that it 
should be placed in the family Microsporaceae of the Ulotrichales. 
In a paper (jointly with Miss Starkey) on Zygneina ericetoruiu and 
the genus Zygogonium, Prof. West pointed out that Kiitzing’s 
genus Zygogonium was entirely synonymous with Zygneina, and that 
Zygneina pachydermum was merely a form of Z. ericetorum —so 
little different that it was scarcely possible to find a single 
discriminating feature. The conjugation of Z. pachydermum is 
quite like that of other species of Zygneina, and since the cytological 
structure of this Alga is absolutely indentical with that of 
Z. ericetorum it may be presumed that the latter also conjugates in 
a normal manner. It was suggested that the two figures given by 
de Bary in 1858 of conjugating Zygogonium didymum (= Z. erice¬ 
torum type), which have been used by Wille and others to uphold 
the retention of Zygogonium as a genus, were merely monstrosities. 
Nobody has ever seen such conjugation since, whereas the West 
Indian form of Z. ericetorum (described under the name of 
Z. pachydermum) conjugates normally. Hence the Zygogonium of 
de Bary and Wille must be dropped. All previous accounts of the 
cytological structure of the cells were found to be inaccurate. 
Mr. S. P. Wiltshire described the biology of the apple canker 
fungus ( Nectria ditissima), which is a genuine wound parasite. The 
normal reaction of the cortex to injury is the formation of a 
phellogen layer over the exposed area, and therefore inoculation 
can only be successful when the injury is deep enough for the 
fungus to reach the wood, otherwise the diseased portion is 
surrounded by the phellogen, the tree thus healing itself of the 
disease. The fungus travels across the cortex through the inter¬ 
cellular spaces, across the phloem and cambium by mechanically 
breaking through the cell-walls, and then traverses the woody 
elements and pith through the pits in the walls. The medullary 
rays do not form a special means of entrance to the wood. The 
reactions of the host against the disease are the formation of (1) 
phellogen, at the limits of the infected region in the cortex ; (2) 
abnormal wood of cells very similar to those of the medullary rays 
and containing gum-sacs ; (3) wound gum in the vessels, though 
this substance can be penetrated by the hyphse. 
Prof. A. H. R. Buller gave an interesting account of the 
hymenium in Coprinus, with special reference to the dispersal of 
the spores, and explained the remarkably effective mechanism by 
which the differing lengths of the basidia bring their spores to 
different levels on the surface of the gill and thus facilitate efficient 
spore shedding. 
