12 THE GENUS PHOEADENDRON 



tropical species as P. chrysocarpum, said to have white or yellow berries 

 when fresh, have the fruit represented in the herbarium with a dull 

 leathery looking surface, the epidermal cells of which have a brassy glint 

 as on other young parts of these plants. The pulpy red berries of P. 

 rubrum, more or less blackened when dry, are distinctly reticulate under 

 a lens by the outlines of their small epidermal cells, and if, as in P. com- 

 mutatum, these are convex, a velvety-dullness is imparted by them to 

 the surface. P. emarginatum and its allies, as well as P. Eggersii and 

 a few other tropical species, have the surface of the fruit distinctly 

 warty : such warts may be more or less confluent into wrinkles, and in 

 P. Grisebachianum the pulp becomes very deeply wrinkled. This sug- 

 gests a range of characters as yet to be made out with sufficient certainty 

 for safe application as differential. Another fruit character that will 

 doubtless prove of much taxonomic value should be derived from the 

 seed and its investing coat of fibres (PI. 10), between which and the 

 outer skin lies the mass of viscid pulp for which mistletoes have long 

 been known : in shape and size this appears to differ considerably when 

 different species are compared, but its utilization must rest on compara- 

 tive study of the mature fruits of many species. In most species the 

 ripe fruit is globose, often varying into ellipsoid as in some of our south- 

 ern mistletoes, or egg-shaped, as in P. chrysocarpum, depressed and 

 elongated modifications of these forms being frequent. Sometimes, but 

 it is hard to tell how constantly or characteristically, a short neck with 

 sub-parallel sides is noticeable, as in P. calif ornicum (PI. 8). Rarely, 

 as in P. acinacifolium and its allies, the fruit is distinctly elongated, the 

 ellipsoid or ovoid fruits of other groups being not much longer than thick , 

 and in P. trinervium, which ultimately has nearly globose berries, the 

 partly matured fruit is similarly lengthened. Usually the berries are 

 glabrous, but in some of our western species they or their sepals are 

 somewhat hairy ; and P. Robinsonii, P. Palmeri, and a few other tropical 

 species, have retrorsely hirsute berries. When the fruit of P. villosum 

 is compared with that of P. flavescens, the sepals with which the berry 

 is crowned are seen to be ascending and somewhat separated in the 

 former, but closely inflexed and meeting in the latter, a difference 

 observable everywhere, the erect or widely parted sepals of such species 

 as P. acinacifolium, P. trinervium and P. Eggersii being especially 

 noticeable (PI. 8, 9). 



SCALES. One of the characters most available and significant in the 

 classification of the species of PTioradendron is a fundamental difference 

 in their leaves. By far the larger number of species have unmistakable 

 foliage, but our western group to which P. calif ornicum and P. juniper- 

 inum belong have their leaves reduced to short thin scales (PI. 4) which 

 resemble those of the related genus Arceuthobium or Razoumofskya so 



