98 



ON A PECULIAR FORM OF MILDEW IN ONIONS. 



Attention should be directed first to the phenomena of growth 

 and propagation, and then to the discovery of some means of 

 prevention or of cure. 



I have said before that onion mildew does not in my opinion 

 arise from bad cultivation, or from peculiarities of soil, though 

 it may be aggravated by either. The probability is that the 

 remedy must be directed to the seeds. It is, however, possible 

 that all our pains may in the end be baffled by these minute 

 plagues. " Few things are more wonderful or more humiliating 

 to man than his powerlessness in contending against God's army 

 of small things, insects and fungi : he can subdue the monster 

 of the sea, and tlie wild beast of the forest, but is conquered in 

 his turn by a tiny fly or a few grains of dust." 



Note. — The species of Mucor may be thus characterized : — 



Mucor subtilissimtis, n. sp. ; mycelio repeiite ; floccis fertilibus ramosis, 

 ramis brevibus patentibus spovangio omnino microscopico terminatis ; vesi- 

 culis demum evauidis : sporis oblongo-ellipticis.. 

 Fig. 1. Mycelium of Mucor subtilissimus highly maguified. A single 



branchlet has pushed into the air, and has produced a sporangium. 

 Fig. 2. Slice from the stem of a diseased onion sending otf abundant 



fructifying shoots, magnified to the same degree as the last. 

 Fig. 3. A portion more highly maguified, showing the various states of 



fructification. 

 Fig. 4. Transverse section of the Sclerotium, showing the dark outer coat of 



two contiguous masses, and the mycelium between them. The lighter 



portion represents the tissue of the interior of one of the masses. 

 Fig. 5. Slice from surface of Sclerotium more highly magnified, with the 



mycelium springing from it. 



a. Mycelium springing from substance of Sclerotium. 

 Fig. 6. Penicillium candidum, exhibiting external aud internal fruit. 



