MISCELLANEOUS CROPS. 145 



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

 should 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 {Heracleum sphondylium), and wild 

 chervil {AntJiriscus cerefolium). (2) Sow perfectly 

 sound seeds. 



(4) The Parasites of Cucdmbees {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 {Thrijos cucumeris?) often 

 causes considerable damage to cucumber plants. It be- 

 longs to the same genus as Thrips cerealium already 

 described. 



The Cucumber Root Fungus ( TJstilago cucumeris, 

 Pig. 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 surfaces (Fig. 49) ; and from 

 a CLuantitative 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. 



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



L 



