CHARACTEES SCALES, CATAPHYLS 13 



closely that species of either genus are commonly to be found in herbaria 

 as representative of the other. Unlike typical foliage leaves, these scales 

 do not disarticulate, though a constriction at the base of the scales in 

 two forms (PL 3) affords partial ground for their specific recognition: 

 one species of the Mexican mountains, P. minutifolium, has almost 

 equally small if fleshy disarticulating leaves: and two of the South 

 American species, P. tunaeforme and P. fragile, are characterized by 

 bearing small scale-like leaves only, a character also encountered in 

 the related genus Dendrophtlwra. 



CATAPHYLS. If any species of the United States, for example P. 

 Eatoni of the everglades of Florida, is compared with any West Indian 

 or South American species, for example P. rubrum of the Bahamas, the 

 latter will be found to possess constantly in addition to its foliage one 

 or more pairs of scale-leaves at least on the lowermost joint of every 

 branch. Comparable with the scales of the flowering spikes and with 

 the stem-scales of P. juniperinum etc., these cataphyls afford by their 

 presence or absence what proves to be one of the most important char- 

 acters for the primary division of the genus Phoradendron. Usually 

 cataphyls do not subtend flowers or spikes, apparently serving no func- 

 tion further than the protection they may afford the shoot in its earliest 

 development; but in P. crassifolium and P. craspedophllum spikes are 

 regularly and characteristically found in the axils of some of the cata- 

 phyls, and less characteristically in a few other cases. 



Never found in any species of the United States, absent from three- 

 fourths of those of Mexico and Central America, but invariably present 

 in all of the South American and West Indian species, these scales are 

 usually confined when present to the basal joint of each branch, though 

 in cases of true or cymose forking they are found on all joints since 

 only basal joints are then present. In a very small percentage, only, 

 of the tropical species with percurrent or monopodial branching, e. g. 

 P. flavens and P. crassifolium and their allies, cataphyls are found on 

 all foliage internodes ; and in a single known species, P. paradoxum, the 

 stem is made up of rather terete joints with cataphyls and ancipital 

 joints without them, in regular alternating succession. 



PARASITISM, HOSTS AND ENEMIES 



All of the species of PJioradendron are parasitic. In the rather few 

 cases in which they are considered as noxious parasites interest centers 

 about the trees on which they occur, though their fruit is said to be 

 poisonous*. Unfortunately the hosts of a very large part of the tropical 



*Cf. Bray, W. L. The mistletoe pest in the southwest. Bull. no. 166, Bur. PI. 

 Industry, U. S. Dep. Agr. 1910. Hedgcock, G. G. Notes on some diseases of trees 

 in our national forests. V. Phytopathology, vol. 5. p. 175-181. June 1915. Pam- 

 mel, Manual of poisonous plants, p. 106, 415-6, 836. f. 196. 



