178 



Broom-Rape. 



[JUNE, 



flowering taking place from June to August. The flowers 

 occur in dense spikes. It is found in Great Britain from 

 Dumfries southward, in Ireland, and in the Channel Islands. 

 On the Continent it is found in several countries. It is 

 parasitic on the roots of a few shrubby leguminous plants, 

 such as broom and gorse. 



i 0. ramosa, Linn. — Hemp is occasionally infested with this 

 species, whilst on the Continent it attacks tobacco. It is 

 figured by Thaer* as brownish in colour, with light blue 

 flowers, and is said to bloom in September. According to 

 Kirchnert the stems are pale yellow in colour, and the flowers 

 light blue or white. 



Other Species. — Several other species occur in this country, 

 but they are of little importance. 0. caryophyllacea, Sm., is 

 found in Kent on Galia, Rubi, &c. 0. rubra, Hook, the flowers 

 of which are odorous, may be found from Ross to Cornwall 

 on Thymus. 0. purpurea, Jacq. (= O. caerulea, Vill.) is a local 

 species in Herts and Norfolk and Hants to Cornwall. It is 

 said by KirchnerJ occasionally to attack Yarrow (Achillea 

 Millefolium). 0. Hederae, Duby, is confined to ivy as its 

 host. 



Description of Seeds. — The seeds of broom-rape are 

 exceedingly small and light, almost dustlike, and are con- 

 tained in two-valved, many seeded capsules. Percival§ says 

 several hundred seeds are produced from a single flower, while 

 Sorauerl| quotes Wentz as having seen 70 to 90 seed-capsules, 

 containing on an average 1,500 seeds, on a single plant. Since 

 they are so small, the seeds of this parasite may be separated 

 with ease, from clover and other agricultural seeds. When 

 shed from the capsules, however, the seeds are easily dis- 

 tributed by the wind. 



Life History. — It may be said at the outset that the seeds 

 •only germinate on coming into contact with the roots of a 

 .host plant. Some species are confined to one host, while others 

 are found on various plants. The following remarks refer 

 ^especially to 0. major, Linn. (= O. elatior, Suit.) and 0. minor, 



* Landwirtschaftliche Unkrauter, Dr. A. Thaer, 3rd Ed. 1905, p. 34. 

 t Op. cit., p. 317. 



* Op. cit., p. 259. 



§ Agricultural Botany, John Percival, p. 559. 

 || Op. cit., p. 21. 



