11 LORANTHACEiE CORNACE^ 217 



sticky pulp. The seed is carried by birds, and wheu 

 dropped adheres firmly to the bark, into which the 

 young plant drives its suckers, which ultimately become 

 thickened to wooden pegs. Unlike many other parasites, 

 the Mistletoe is partly green. This has been accounted for 

 by suggesting ^ that it only takes the ascending sap, while 

 the brown parasites make use of the descending, elabor- 

 ated sap, and consequently can dispense with green 

 leaves. This, however, is probably incorrect, for not 

 only does the Mistletoe root become firmly fixed in the 

 wood of its host, thereby tapping the stream of water 

 and dissolved substances rising from the roots, but also 

 develops secondary branches which make their way along 

 the bast, that is, the path of the descending sap. The 

 evergreen leaves well serve for the construction of carbo- 

 hydrate in the winter, when in most cases the host 

 plant will have shed its leaves. Hence the relation 

 between Mistletoe and host becomes one of symbiosis, 

 involving, that is, a certain mutual advantage. 



The leaves have no palisade cells, the tissue between 

 the upper and lower epidermis being fairly uniform 

 throughout. 



It is fertilised by insects (bees and flies), and is 

 therefore interesting as a species which is dependent on 

 both birds and insects. 



COENACE.^ 

 CORNUS 



We have two species — 0. suecica, a low herb, with 

 4 petal-like bracts ; and C. sanguinea, a shruli, with- 

 out bracts. The flowers are homogamous, with free- 

 lying honey secreted by the base of the pistil. 



0. sanguinea. — The anthers open inwards, and at 

 the same level as, but some little distance from, the 

 pistil ; so that an insect visiting the flower is almost 

 sure to dust itself with pollen on one side, and to touch 



^ Constaiitin, La Xature Tropicalc, 



