1906.] 



Dodder. 



331 



DODDER. 



The question to what extent the various species of dodder 

 are harmful to agricultural crops is one which is of considerable 

 interest to the farming community, and for some years past the 

 agricultural press has contained many references to the pre- 

 valence of the pest in various districts. Moreover, in 1905, as 

 much as 1 1 per cent, of the clover seed samples examined by the 

 Botanist to the Royal Agricultural Society were condemned 

 owing to the presence of dodder seeds, while two samples of red 

 clover contained no less than 6 per cent. Some information, 

 therefore, on the several species of dodder, the methods by 

 which they are spread, and the best means by which they may 

 be suppressed or avoided, may at the present time be of value 

 to agriculturists and seed merchants alike. 



Description of Certain Species of Dodder. 



Some eighty species of dodder are known to science, and 

 of these several occur in Britain. Dodder is botanically 

 included in the order Convolvulacece under the genus Cuscuia. 

 The dodder plant is an annual, growing from seed either self- 

 sown or sown with other seed, and it is parasitic on other plants 

 of a higher order, germination, however, taking place in the 

 soil. Four species or varieties are mentioned in Hooker's Flora 

 of the British Islands, these being Cttscuta europaea, C. epilinuin, 

 C. epitJiyniHiH, and C. irifolii, the most important being 

 C. trifolii. Other species, however, which have been introduced 

 with imported clover and other seeds, may cause m.uch damage 

 in European countries, these being C, corymbosa (of American 

 origin), C. Gronovii (also American), and C. monogyna. All 

 species are parasitic on other plants, and all have the same 

 meth'od of reproduction. 



Cuscuta trifolii. — This species (PL I.), significantly termed 

 clover dodder," and, according to Hooker, a variety of C. epithy- 

 }nnm, is the species commonly met with. It chiefly attacks red 

 clover and lucerne. After a seed has once germinated the seed- 

 ling quickly dies, unless a clover or other suitable plant be at 

 hand, but, once established on a plant, it sends out roots or 

 suckers (haustoria), which take firm hold of the host, loses its con- 

 nection with the soil, and thereafter, unless checked, will rapidly 



