410 Mr. Bowman on the Parasitical Connection 



am therefore inclined to believe that the pale and sickly hue of 

 such parasites, whether fixed on roots or stems, results at least 

 as much from this circumstance as from the surreptitious nutri- 

 ment on which they feed. The absence of true leaves consti- 

 tutes one essential physiological distinction between Cuscuta and 

 Viscum ; and though Listera JSlidiis avis, Monotropa, and Orobanche 

 are parasitic on roots, they are also destitute of leaves furnished 

 with pores. All such plants are consequently incapable of draw- 

 ing sustenance from the atmosphere, and of being acted on by 

 the powerful stimulus of light, and can only derive the necessary 

 supply of food through the medium of their lower extremities. 

 It may be said that as they find their food ready provided for 

 them by the stock on which they grow, leaves would be super- 

 fluous ; and that Nature, in depriving them of these usual organs 

 of assimilation, has, in the plenitude of her power, prepared it 

 for them through the medium of a foreign source. But this 

 does not explain the cause of the absence of green colour ; in- 

 deed the instance of the Misletoe renders the reasoning incon- 

 elusive. This plant is perhaps more strictly parasitical than 

 any of those just named, yet it is green ; — a necessary conse- 

 quence, as I conceive, of having leaves, though they be sparingly 

 supplied with pores *. 



I hope to make it appear that the Lathraa differs in struc- 

 ture from all the parasites just named; and that, though it be 



* 1 lia^'e observed that the Misletoe dies with the tree on which it grows ; and from 

 a notice in the Magazine of Natural History (vol. ii. p. 294.), it seems that the La- 

 thraa does so too. It has long been doubted whether Listera Nidus avis be strictly 

 l)arasitical. Whatever it may be in the earUer stages of its growth, it certainly is not 

 so in its more advanced state. If it be carefully got up in a clod, and the soil after- 

 wards washed from around it, the base of the central root or caudex may be seen to 

 terminate in a short curved spur, which tapers to a fine point, and evidently is not at- 

 tached to any other vegetable. The cuticle of the stem and its bracteas has no per- 

 spiring pores. 



parasitic 



