FUNGOID PESTS OF CULTIVATED PLANTS. 89 



The Hop mildew and the Rose mildew belong to the same family of 

 parasites. 



These fungi are, in the first instance at least, true epiphytes, making 

 their appearance on the surface of the leaves before there is any infection 

 or disease of the host-plant, and, as such, are more amenable to 

 treatment. 



Dry weather in the case of these fungi is usually considered as pro- 

 pitious to their development ; hence it follows that wet checks develop- 

 ment, and syringing or watering the leaves in dry seasons is the best 

 moderator of its evil influence. 



Sulphur is doubtless of considerable service, as it has been in the Hop 

 mildew. 



Sacc. Syll. i. No. 73 ; Smith, Field Crops, p. 266 ; Cooke, M. F. 220, 

 figs. 237-9. 



Parsley Leaf-spot. 

 Septoria Pctroselini (Desm.), PL VII. fig. 112. 



The leaves of the Parsley and sometimes of the Celery are liable to 

 become spotted with this disease. It shows itself scattered over the 

 surface in little spots, which are at first brownish and then bleached, so as 

 to become almost white in the centre. Scattered over these spots are the 

 little dot-like receptacles, or perithecia, which contain the sporules, the 

 spots being already permeated by the mycelium, which produces the dis- 

 coloured spots. 



The sporules are long and narrow, thread-like, with a row of small 

 nuclei, and these escape when mature, like a small tendril from a pore at 

 the apex of the receptacle (35-40 x 1-2 fi). 



When the leaves are moistened and the dew is upon them, the little 

 tendrils ooze out and soon dissolve, so that the sporules may be dis- 

 seminated over the leaf. 



A shower of rain, or watering artificially, may transfer these sporules 

 to other and healthy leaves. 



This species is recorded as known in France, Belgium, Italy, Germany, 

 and S. America. 



Sacc. iii. 2876 ; Mass. PL Dis. 270. 



Celery Brand. 

 Puccinia Apil (Corda), PI. VII. fig. 113. 



Sometimes the Celery rust finds its way into gardens, where it soon 

 creates mischief, disfiguring the leaves and stunting the plant. It has 

 been proved that it is capable of being introduced through the medium of 

 seed obtained from diseased plants. 



The appearance of this pest on the foliage is first detected by swollen 

 paler spots, and soon afterwards the cuticle is broken irregularly over 

 each of these spots or pustules, and the brown powdery spores escape 

 from the fissures like snuff and become sprinkled over the leaves. 



It is customary, in these latter days, to regard the above as one of the 

 forms of Puccinia bullata, but we prefer to retain the above name as a 

 distinction for a definite disease. 



