14 THE GENUS PHORADENDKON 



species remain to be noted and observers and collectors who interest 

 themselves in the genus in the future will do well to pay particular atten- 

 tion to this point. 



So far as I know, none of the representatives of this genus attack 

 either tree ferns or Monocotyledons, and relatively few are found on 

 Conifers : the majority affect woody Dicotyledons. Though sometimes, 

 as in the case of our common mistletoe P. flavescens, occurring on a num- 

 ber of unrelated hosts, most of the species appear to be restricted in 

 this respect, though to what extent is to be shown, rather than inferred 

 from the scanty information now at hand. The oak, known in connec- 

 tion with the European mistletoe rather from its infrequency as a host 

 than because it is often seen to support the parasite, is one of the most 

 frequently attacked trees on our own continent except in the Northeast ; 

 and in the Southwest the sycamore, mesquite, cottonwood, hackberry 

 and elm are much parasitised. Though the European Viscum sometimes 

 occurs on Conifers, these trees, which support the related genus Arceutho- 

 bium or Razoumofskya in abundance, appear to be attacked by only a 

 limited number of species of Phoradendron which constitute a well- 

 limited group, the ' ' Pauciflorae, " and this group is strictly confined to 

 Conifers except for one species, P. calif ornicum, which affects a variety 

 of Angiosperms but no Gymnosperms, and P. Bolleanum which, in addi- 

 tion to coniferous hosts, has been collected on Arbutus. The succulent 

 Cactaceae support one species, P. Kuntzei. 



Secondary parasitism is not at all unknown in the genus, though re- 

 stricted to its tropical species, one group of which, the ' ' Amplectentes, ' ' 

 exhibits this trait markedly. Except when they serve as hosts for other 

 mistletoes, the Phoradendrons do not appear to suffer much from the 

 attacks of parasites. I have seen a single collection (P. antttlarum) 

 in which a mistletoe was overgrown by Cuscuta. Few fungi are known 

 for them even when dead ;* and the number of insects known to attack 

 them is very limited,! though some southwestern collections are badly 

 infested by scale insects. 



ORIGIN OF THE GENUS 



Questions as to the origin of families like the Loranthaceae are doubly 

 difficult because complicated by parasitism and attendant reduction. Of 

 a group of families with little-differentiated ovules and seeds which Van 

 Tieghem has brought together under the name " Inseminees, " the Loran- 

 thaceae give every indication of tropical Asiatic origin, and the family 



*Cf. Saceardo, Sylloge Fungorum, host index. The related genus Arceuiholium 

 is likewise free from fungi. Cf. Weir, Journ. Agr. Eesearch. vol. 4. p. 369. 

 }Cf. Schwarz, Proc. Entomol. Soc. Washington, vol. 4. p. 397. 



