WEEDS— PECULIARITIES AND DISTRIBUTION 433 



chlorophyll in these is deficient, probably in quantity and also 

 in quality, so that the plant is unable to assimilate sufficient 

 carbon to supply itself with all the food it requires ; conse- 

 quently, a parasitic habit of life has been adopted, the plant 

 living largely at the expense of certain hosts. It is usually 

 found in pastures parasitic on the roots of grasses ; the plant 

 is generally of small stature and is sometimes classed as a 

 distinct variety — Rhinanthus minor. A larger variety, R. major, 

 occurs among cereal crops, where it may do great damage. 1 

 The plant possesses fibrous roots which develop fairly 

 large spherical suckers and these attach themselves to the 

 roots of the host plant. Absorption cells are developed on 

 the suckers which rob the host of nutriment, in aggravated 

 cases causing them to die of starvation. Even when the plant 

 is not killed off, it is very much impoverished by the drain 

 instituted by the parasite. The Rattle may do harm in another 

 way. Large quantities of seeds are produced which fall in 

 close proximity to the mother plant. Consequently thousands 

 of seedlings spring up within a small area just at the time when 

 the young plants of the crop stand most in need of light and 

 air, so that the latter are stinted in these essentials and do not 

 flourish so well as they otherwise would do. 



3. Lesser Broomrape. — This plant again is a total parasite 

 but of a type quite different from that of the Dodder. The 

 plant consists of a sturdy stem of a dirty brown or purplish 

 colour, with scales to match ; no true leaves are produced and 

 no chlorophyll. Each stem bears a spike of flowers resembling 

 it in colour, each flower being furnished with a bract similar 

 to the scale leaves ; numerous small seeds are produced. 

 Instead of possessing a true root, the base of the plant is 

 swollen just where it is attached to the roots of the host plant, 

 which belongs characteristically to the order Leguminoseae, 

 clover being a very general victim. The connection between 

 the tissues of the host and parasite is so intimate that it is 

 usually a matter of difficulty to distinguish between the cells 

 of the two. Kerner and Oliver 2 state: 



1 A field of Barley at Heytesbury (Wilts) was so infested with Yellow Rattle 

 this year (191 1 ) that in many parts of the field the barley had practically dis- 

 appeared, the plants being absolutely stunted. In other places where a certain 

 amount of vegetative growth had been made, the plants failed to come into ear. 



2 A. Kerner and F. W. Oliver, Natural History of Plants, vol. i. pp. 184-5. 



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