PARASITIC PLANTS 265 



seeds are readily scattered by the wind, but are easily 

 separated from clover seed samples. 



The life history of Broom-rape is interesting, for the 

 seeds only germinate on coming into contact with the 

 roots of a host plant, and some species are parasitic on 

 but one host, while others attack a number of plants. 

 In the case of O. minor the seedling on germination 

 is thread-like, and somewhat resembles that of Dodder. 

 It attaches itself to the roots of its host by means of a 

 sucker, develops a fleshy stem which "grows upwards 

 through the soil, appearing above it like a pale, 

 brownish-red asparagus shoot from 6 inches to 18 

 inches in length." The spike of flowers is then pro- 

 duced. 



According to a Leaflet * issued by the Swiss Experi- 

 ment Station, when the summer is warm and dry the 

 seedlings grow rapidly in the first year, building up 

 until autumn an onion-shaped, scaly rootstock with 

 a large number of roots, which endeavour to attach 

 themselves to other clover roots. No shoots come 

 above ground in the first year, but they appear in 

 the second year, after the clover is cut. (In this case 

 the Broom-rape would be a biennial.) Owing to the 

 storing up of food in the clover plants after the clover 

 is cut, and the extra warmth of the now bare soil, 

 growth of the Broom-rape is very rapid, and the flowers 

 appear in a few days. In an extraordinarily short time 

 the seeds are ripened and distributed by the wind. 



As regards prevention and remedy, the following sug- 

 gestions may be made : 



i. Although the seed of Broom-rape is so easily 

 separated from clover seed samples, it may sometimes 

 be found in such ; and Percival quotes a case in which 



1 Fliigblatt Nr. j", Schweizerische Samen-Untei sucklings- und Versitchs- 

 anstalt Zurich. 



