6 On the Nourishment produced to the Plant hj its Leaves. 



but besides this it has a hollow pointed vessel or instrument which 

 only tills lip the veiy ceri/re ot" the middle, the rest between 

 the centre and broad piece remaining a perfect vacuum. This 

 point runs deep into the supporting plant, drawing from it a per- 

 petual stream ; and thus possessing itself of all the nutriment re- 

 quired, \^hile the vacuum surrounding it is perpetually main- 

 tiiined by the superior force of the larger vegelaide. I have ex- 

 amined the pointed part inserted into the mother plant (see 

 fig. 9) at different degrees of dcplh ; and in the dodder tribe it is 

 so very clear that its insertion is most easily to be perceived, though 

 entering far into tbc plant, especially if the furze is yonng and 

 tendei-. This description will, I fear, ajjpear rather ol)scure ; but 

 the drawings, see tig. 8, 9 and 10, will I hope elucidate it. 



There are a great variety among the parasite jilants : solne, like 

 the ivy, are half fed by the root, half by the nurse plant to wbich 

 they cling. Some, like the orobunche, fix their roc.t ov the iivrse 

 plant that is to feed it. But though it seems to draw all its 

 nourishment from the plant to which it adheres : yet much of 

 its support is gained from the earth, on which its large and 

 spreading roots repose : it has many fixed appendages growing 

 from the root, which appear to me to play the oflice of a sponge^ 

 and suck up much moisture, which it undoubtedly yields to the 

 plant, since all the vessels of coinmunicalion with the real root 

 appear. But there is a peculiar circumstance belonging to this 

 plant which should not be overlooked : it possesses such -a 

 quantity of tannin, that my hands were absolutely dyed for a 

 long time after dissecting it. I am well assured that the quan- 

 tity of tannin is not always proved by the excess or depth of the 

 colouring matter, and that there may be much of the latter^ 

 with little of the former, as in the alder : but I believe when it 

 \'^ fixed aitd difficult to eradicate, and that it has a glazed ap- 

 pearance, the quantity of tannin always predominates. Tlie 

 orobanches (especially in a sandy soil) grow in such quantities, 

 and their roots are so large, that to collect them might be 

 no bad speculation, since there is often a pound of root to each 

 small plant. 



The dodder tribe presents another variation of the parasite. 

 It soon loses its root, and de]5ends on the joint aid of the nurse 

 plant and atmosphere ; its pump is nearly the same as that in 

 the ivy, but it is only a small jucce of the stem that draws mois- 

 ture from the atmosphere. The flower itself, however, never 

 closes after it has once opened, and constantly exposes its most 

 curious pointed nectary (it should seem) for this purpose, since 

 it is always loaded with diminutive specks of water on the 

 projecting points. Thus there are various means of nourishment 

 made use of by nature in this species of plants : some gain from 



the 



