72 DISEASES OF CULTIVATED PLANTS 



attacked by O, ramosa, but they yielded as good a crop of 

 fruit as neighbouring plants not attacked. O. minor proves 

 injurious to clover when present in abundance. 



As Bentham remarks, the species are in general difficult to 

 characterise. Some appear to thrive only on the roots of one 

 species, or at most two or three closely allied ones, whilst 

 others will grow on a great variety of plants of the most 

 remote natural affinities. But as the particular stock the 

 plant feeds on occasions some modification in the habit of the 

 parasite, it is in many cases a matter of great doubt whether the 

 differences observed are owing to this circumstance or to real 

 specific distinction. It is not therefore improbable that some 

 of the species here adopted, although much less numerous 

 than those usually distinguished, may on more careful obser- 

 vation prove to be mere varieties of each other. 



Tooth wort (Lathraea squamaria, L.) is a pale rose-coloured 

 plant, with dingy, flesh-colouretl, or slightly bluish flowers, 

 streaked with purple or dark red. Rootstock, fleshy and 

 creeping, covered with close-set, thick, fleshy scales. Flower- 

 ing stems erect, from four to nine inches high, with a few 

 broad, orbicular scales gradually passing into the floral bracts. 

 Flowers in a dense spike. Flowers in early spring. 



Parasitic on the roots of hazel, beech, hornbeam, elm, 

 alder, etc., but not causing any material injury. 



The dodders, of which some eighty kinds are known from 

 different parts of the world, are all annual parasitic plants with 

 very long, thin, thread-like, leafless stems which twine round 

 the stem and branches of the plant they are parasitic upon. 

 The small, wax-like flowers are produced in round clusters, 

 and are usually white, suffused with a more or less distinct 

 reddish flush. The stems are red or yellowish, and there is 

 no trace of green present anywhere. The seed germinates in 

 the ground, and the young seedling is supported for some 

 little time by the reserve of food contained in the seed, but if 

 it does not attach itself quite early to a suitable host-plant it 

 perishes. If a plant that the dodder can grow upon happens 

 to be close by, the young dodder plant on coming in contact 

 with its host, twines round its stem, and at short intervals 

 sends in suckers, which absorb nourishment and enable the 

 parasite to grow along with its host. After the parasite has 

 once gained possession of a host its root in the ground 

 perishes and it afterwards depends entirely on its host for 

 food. As host and parasite continue to grow the latter 



