FIELD AND FOREST. 67 



wood? or is the Mistletoe incapable of growing except where there 

 are pre-existing cavities — perhaps made hy worms — which its roots 

 may enter ? or, finally, may we suppose that v.hile the Mistletoe is 

 unable to penetrate beyond the bark of the Pepperidge, a subsequent 

 deposit of wood surrounds and covers the base of the twig ? The 

 last hypothesis seems to me most probable. 



The twigs of Mistletoe always, or nearly always grow in clusters! 

 Does each twig grow from a separate seed ? or is a single seed capa- 

 ble of producing a cluster ? 



These clusters always grow on swellings of the wood of the Pep- 

 peridge. Does the Mistletoe cause the swellings? or is it incapable 

 of growing elsewhere ? I strongly incline to the former view In a 

 tree badly infested by Mistletoe, clusters of short twigs may be seen 

 growing on small swellings, and clusters of long twigs on large ones, 

 as if the swelling had grown with the twigs ; and very large swellings 

 ba.re of Mistletoe terminate the ends of dead branches, as if they, too, 

 had once borne a crop of Mistletoe, and been overloaded and killed 

 by it. 



M. H. DOOLITTLE. 



Palms and Yuccas of the United States. 



The Palms, although principally tropical products, are yet sparingly 

 represented within the limits of the United States. In structure, they 

 belong to the class Endogens or Monocotyledons, which in the tree grow- 

 ing species are characterized by a straight cylindrical, generally un- 

 branched trunk, surmounted with a large terminal cluster of generally 

 compound stalked leaves, which are more or less expanded at the base, 

 and partly sheathing the stem. The exterior is not clothed with a 

 distinctly separable bark, nor with concentric circles of woody matter, 

 as in Exogens, but is at first covered with the decayed and adhering 

 leaves, which, however, finally fall off, and leave a smoothish surface, 

 and the woody matter exists in long fibrous bundles, imbedded at 

 first loosely in the cellular tissue, and finally becoming condensed 

 and solid from the formation of new woody bundles at the centre 

 which crowd toward the surface the older formed ones, thus causing 

 the oldest and hardest wood to be at the circumference, instead of near 

 the centre as in Exogens. 



