PARASITES 127 



by a small hole on the under side near the base. The 

 walls of these chambers are covered with peculiar capitate 

 hairs, which at one time were looked upon as glandular, 

 secreting a digestive fluid for the purpose of consuming 

 the bodies of minute animals which were unfortunate 

 enough to find their way into the chambers. In this way, 

 it was said, the plant obtained a supply of nitrogenous 

 food. But it is now known that the toothwort is not an 

 insectivorous plant at all ; the capitate hairs are water- 

 secreting structures water-glands. The entire plant 

 lives underground in soil where the atmosphere is 

 always moist. Transpiration is, under these circum- 

 stances, small, and the plant finds it difficult to get rid 

 of excess of water. This is especially so in spring, when 

 the roots of the host are drawing a large quantity of water 



FIG. 41. Lathrcea squamaria (TOOTHWORT), SHOWING UNDERGROUND 

 SHOOT BEARING SCALE-LEAVES, ATTACHED TO THE ROOTS OF HAZEL 

 BY ABSORBING SUCKERS (a). (AFTER KERNER.) 



To the right a section through one of the hollow scale-leaves. 



from the soil for the use of the opening buds and expand- 

 ing foliage. The supply of water to the parasite is conse- 

 quently equally vigorous, and the plant gets over the 

 difficulty by excreting the excess in liquid form by the 

 glandular hairs. In June long spikes of pale, flesh- 

 coloured flowers grow up through the soil into the air, and 

 as these are the only parts that ever appear above ground, 

 the plants are difficult to locate except when in flower. 

 Glands similar to those found in the leaves of the tooth- 

 wort occur in the subterranean buds of certain hemi- 

 parasites e.g., Bartsia and may serve a similar purpose. 

 (2) Orobanche. This genus includes several species, 

 nine of them British. They are brown scaly plants, 

 attached to the roots of various hosts, such as grass, ivy, 

 hemp, clover, etc. Some species confine their attention 



