1893.] MICROSCOPICAL JOURNAL. 35 



nation takes place in water, whether in artificial culture or in a 

 drop of water on the surface of a leaf of the host-plant, the germ - 

 tubes are very slender, equal, simple, or sparingly branched, 

 spirally curved, transverse septa very rare, and the fusion be- 

 tween original^ distinct tubes or branches very rare, or in most 

 cases entirelv absent (Figs. 4 and 5). About two days after 

 germination has commenced, one or more short, lateral l")ranches 

 spring at right angles from the germ-tubes ; these may be con- 

 sidered as specialized sporophorcs. The apex of each sporo- 

 phore becomes slightly incrassated, and within a day produces 

 several simple or branched concatenate chains of elliptical, pale 

 olive, smooth secondary spores. These secondary spores are 

 developed in acropetal order (Fig. ■^a). 



When the spores germinate in a sterilized solution of the host- 

 plant i^Smilacina stellata)^ the germ-tubes measure 5-6// in 

 diameter at the point of origin from the spore, become elongate, 

 never spirally twisted, and gradually taper to the apex ; trans- 

 verse septa are abundant ; the clusters of secondary spores are 

 about equal in number, and the secondary spores of the same 

 size as those produced on the very slender germ-tubes formed by 

 spores germinating in pure water (Fig. 3). In both instances 

 sporophores bearing clusters of secondary spores are not un- 

 frequently produced directly by interstitial cells of the spore 

 without the intervention of a germ-tube (Fig. 3(7+ '^^id Fig. 



5^+)- 



Throughout the summer months the spores germinate as soon 



as mature, at the ordinary temperature of the air ; but the later 



batches of spores produced in September and October will not 



germinate, or very feebly, at the temperature of the air ; such 



spores remain passive during the winter, and germinate the 



following spring. Nevertheless, these are not resting spores — 



in the ordinary sense of the term — but will germinate at any 



period throughout the winter, provided the temperature is 



sufficiently high. 



During the summer the isolated patches of disease that corre- 

 spond to independent centres of infection increase in size and 

 run into each other, the whole leaf not unfrequently presenting 

 a blackened appearance, caused by the dark-colored hyphte. 



During the autumn the stronger branches of the vegetative 

 hyphae increase considerably in thickness, many of the cells be- 

 coming very much inflated and spherical and separated by deep 

 constrictions, due to the transverse septa not increasing in diame- 

 ter. Many of these stout hyphae become more or less irregularly 

 branched and contorted at the tip, the convolutions approach 

 each other, and by repeated cell-formation produce a more or 

 less globose sclerotium-like body, almost black externally, some- 

 what paler inside (Fig. 11). These sclerotia remain passive dur- 

 ing the winter. In the following spring certain of the external 

 cells of the sclerotia become more prominent than the rest, and 



