MILDEW AND BRAND. 49 



Look down at the green leaves, especially the lower 

 ones, and you will soon find one apparently grown 

 rusty. The surface seems to be sprinkled with 

 powdered red ochre, and grown sickly under the 

 operation. Pluck it carefully, and examine it with 

 a pocket lens. Already the structure of a healthy 

 leaf is familiar to you, but in the present instance 

 the cuticle is traversed with numerous longitudinal 

 cracks or fissures, within which, and about their 

 margins, you discern an orange powder, to which 

 the rusty appearance of the leaf is due. Further 

 examination reveals also portions in which the 

 cuticle is distended into yellowish elongated 

 pustules, not yet ruptured, and which is an earlier 

 stage of the same disease. This is the " rust '^ of 

 the agriculturist, the TricJiohasis riihigo-vera of 

 botanists, the first phase of the corn mildew. 



To know more of this parasite, we must have 

 recourse to the microscope ; having therefore col- 

 lected a few leaves for this purpose, we return 

 homewards to follow up the investigation. We 

 will not stay to detail the processes of manipu- 

 lation, since these will not offer any deviation from 

 the ordinary modes of preparation and examination 

 of delicate vegetable tissues. 



The vegetative system of the " rust,'^ and similar 

 fungi, consists of a number of delicate, simple, or 

 branched threads, often intertwining and anasto- 

 mosing, or uniting one to the other by means of 

 lateral branchlets. These threads, termed the 



E 



