ILLUSTRATIONS OF PHTTOPHTHORA INPESTANS. 417 



marks the previous place of origin of a conidium, which had 

 been thus developed and displaced. 



Fig. 4. — In this drawing the germination of the conidiura 

 and of the zoospores to which it gives origin are represented. 

 The conidium {g) was one of five which had been isolated in a 

 drop of water, suspended in a damp chamber beneath the 

 microscope. The sowing of conidia was taken from fresh, 

 damp, diseased leaves, and made at 11.35 a.m., and the coni- 

 dium {g) was then drawn. The contents were densely granular, 

 and looked dark grey. The cellulose wall was sharply marked, 

 and the pale papilla at the anterior end distinct, but not promi- 

 nent. The short, broken-off pedicel was also evident. The 

 first changes of note occurred at about 2 p.m., when the con- 

 tents appeared much more translucent and watery, the dark, 

 coarse granules being no longer obvious. This seemed to be 

 owing to their having altered in character and become more 

 translucent. The cell wall was also paler, perhaps because the 

 contrast between it and the closely fitting contents was less 

 marked. The apical papilla was thicker, and slightly more 

 prominent. During the next two hours or so (2 p.m. to 4 p.m.) 

 the peculiar hyaline granular contents were obviously under- 

 going changes, and very slow movements of the translucent 

 granules occurred, producing variations in the faint cloudy 

 markings shown in the drawings (A and i). Towards 4 p.m. 

 certain vacuoles appeared, and at length became sufficiently 

 distinct to draw [i). There were about nine of these alto- 

 gether. The papilla also became more prominent, as if it was 

 swelling up. At 4.50 it was obvious that each of the vacuoles 

 formed the centre of an angular block of protoplasm, as seen 

 in k. These angular blocks were separated by thin, sharply 

 marked plates, and the whole mass was no longer close to the 

 outer wall of the conidium, but a pale, watery looking line lay 

 between them. The apical papilla was still more gelatinous 

 in appearance. That these angular blocks were incipient zoo- 

 spores was proved by what followed. Their arrangement ap- 

 peared to be as follows — one at the apex, three in the next tier 

 (two visible in the drawing), four in the next tier (three visible 



