144 



SIX MICRO-PHOTOGRAPHS TAKEN IN CONNECTION WITH THE 

 WARMINSTER EXPERIMENTS. 



A. Pytophthora infestans. SEC- 

 TION OF LEAF OF POTATO WITH EX- 

 TERNAL ORGANS OF P. I. X. 20. Most 



of the conidia have fallen off. It is very 

 difficult to cut and mount sections of 

 leaf without their doing so, but the 

 illustration shows the relative size of 

 the external hyphse compared with 

 the thickness of the leaf and with 

 the leaf hairs. The hyphce, it will 

 be seen, are considerably shorter 

 than the leaf hairs. Fig. 21. 



C. Phytophthora infestans. x. 100. 

 HYPHA EMERGING FROM STOMATA 



OF LEAF OF POTATO PLANT. The 



conidia are out of focus. The second 

 filament, on the right, has the ap- 

 pearance of mycelium, the protoplas- 

 mic matter of which is more granular 

 than that of the hyphse. This speci- 

 men was obtained, after many at- 

 tempts, by detaching a minute por- 

 tion of the under-skin of the leaf 

 with the hypha in situ. Fig. 22. 



