MISCELLAWEVUS CHOPS. 145 



sown. (2) As far as possible, all umbelliferous weeds 

 sh-ould be destroyed. 



Cure. — See those under the heading of Puccinia gra- 

 minis. 



The Celery Mildew {Puccinia heraclei), like the 

 preceding fungus, belongs to the Uredinece. It some- 

 times infests celery plants. 



Prevention. — (1) Destroy all umbelliferous weeds, espe- 

 cially cow-parsnip {Eeracleum sphondylium), and wild 

 chervil {Anthriscus cerefolium). (2) Sow perfectly 

 sound seeds. 



(4) The Parasites of Cucumbees {Cucumis sativa). 



The Cucumber Eelworms {Tylenchus cucumeris?) 

 belong to the Anguillulidce, or "thread-worms." They 

 are said to destroy the roots and rootlets of cucumber 

 plants. 



The Cucumber Thrips {Thrips cucumeris?) often 

 causes considerable damage to cucumber plants. It be- 

 longs to the same genus as Thrips cerealium already 

 described. 



The Cucumber Root Fungus (Ustilago cucumeris, 

 rig. 48) was discovered by the author infesting the roots 

 and rootlets of Cucumis sativa.^ During the summer of 

 1887, Mr. E. F. Crocker (a market gardener, of Ham 

 Green, Bristol) sent the author a large number of the 

 roots of cucumber plants, with " peculiar knot - like 

 bodies " upon their external siu'faces (Fig. 49) ; and from 

 a quantitative estimation of the nitrogen contained in 

 these " swellings," and in the roots proper, the author was 

 at first inclined to believe in the hypothesis of Dr. 



I Proceedings Royal Society of Edinburgh, vol. xv. p. 403. 



L 



