DISEASES OF TREES 



nourishment of the band of cambium situated under the stem 

 of the honeysuckle. 



Triticum repens* may also be mentioned here, the sharp-pointed 

 rhizome of which has the power of piercing and growing through 



the fleshy roots of other plants which it 

 may encounter in the soil. This has 

 been specially observed in beds of oak 

 seedlings, though it may be remarked 

 that the piercing of the roots has re- 

 sulted in no apparent damage to the 

 oaks. 



The passage to the true parasites 

 that is to say, to those which subsist 

 entirely on the plastic materials of 

 other plants is formed by a group of 

 plants in which one cannot at first per- 

 ceive a parasitic existence, seeing that 

 they are provided with leaves containing 

 chlorophyll, and take water and inor- 

 ganic nourishment from the soil with 

 their roots. While they assimilate plastic 

 materials for themselves, they also attach 

 themselves to the roots of other phane- 

 rogamic plants from which they abstract 

 organic substances by means of an absorb- 

 ing apparatus (haustorium) on certain of 

 their roots. To such plants belong the 

 Rhinanthece, a sub-family of the Scro- 

 pliulariacece. The cow'-wheat (Melampy- 

 rum arvense], the common yellow-rattle 

 (Rhinanthus Crista-galli), and the louse- 

 wort (Pedicularis] and eye-bright (Eu- 

 pJirasia) furnish well-known examples 

 of this kind of life. As these plants 



are parasitic only on the plants of pastures and meadows, we 

 cannot here spare time to examine them more closely. The genus 

 Lathrcea, also, which contains the common species LatJircea 

 squamaria, the tooth-wort, has not yet been proved to be wholly 

 * [" Couch grass " or " twitch." ED.] 



