61 



which is connected with the stock plant by tubercles. M. 

 Unger intends to publish his observations on this subject in 

 a separate memoir. 



Highly interesting is the peculiar connexion existing be- 

 tween the roots of Monotropa hypopithys and the roots of the 

 stock plant (Pinus Abies, L.). According to M. Unger's dis- 

 covery, it is a rhizoma-like, tuberose, irregular body, from 

 which the inflorescence of the plant proceeds, and this body 

 consists of a convolution of intimately matted fibrils which 

 belong partly to the parasite and partly to the stock. This 

 root mat is externally somewhat loosely penetrated by earthy 

 masses, but towards the centre increases so much in closeness 

 of texture, that the masses almost entirely disappear, and 

 nothing is left but a tissue of roots which cannot be unra- 

 velled. The contact of the two roots, easily distinguished 

 from each other by form, colour, and consistency, is very in- 

 timate, although no tubercles or similar organs exist, by 

 which a direct union, an interpenetration of both, might be 

 effected. The parasite is therefore nourished in this case by 

 the exudation of the spongioles of the root. It must not be 

 thought that this nourishment consists in the excrements 

 of the roots, for I think I have proved that these supposed 

 excrements are precisely in the same situation as the whole 

 doctrine of spongioles of the root and tuberosities, of which 

 nothing exists in nature. 



M. Unger has also published some very interesting obser- 

 vations on the growth of the Cuscuta. These plants are easily 

 raised if their seeds be sown among green plants already 

 developed. During the first period the young plant daily 

 lengthens about an inch, the original embryo becoming dry up 

 to that point of the stem where the first tubercle makes its 

 appearance. The young germs w r ould not succeed on the green 

 leaves of Sedum album, although the tubercles of the Cuscuta 

 had already become fixed to them. A young Cuscuta with 

 its stock was placed under a glass and kept moist by the va- 

 pour of the water : during three days it increased in size, then 

 made 1 coil round itself and produced tubercles at this very 

 place. The lower part of the plant now ceased to grow, while 

 the tubercles penetrated of themselves into the substance at the 

 entwined spots. M. Unger observed the metamorphosis of an 



