10 THE GENUS PHORADENDRON 



INFLORESCENCE. The essential characters of Phoradendron in its 

 group of Loranthaceous genera are chiefly its axillary spikes of small 

 unisexual and monochlamydeous sessile flowers (PI. 5-6), often sunken 

 in hollows of the frequently swollen internodes of the rachis and nor- 

 mally trimerous (PI. 7), with 2-celled longitudinally dehiscent anthers. 

 A very few species, like P. cymosum, present the phenomenon of a termi- 

 nal spike corresponding to the 1- or few-flowered cyme of the old world 

 Viscum, but in addition to axillary spikes. Except in the species taken 

 by Hooker for falcatum, the receptacular cups, which range from so shal- 

 low as hardly to surround the base of the flower to a depth covering a 

 noticeable part of the mature fruit, are essentially even on their margin ; 

 but in this species the cup is sometimes parted so as to present the ap- 

 pearance of a deeply divided calyx. The flowers, with a small vestigial 

 nectar gland and apparently adapted to pollination by such short- 

 tongued insects as flies and small bees,* are usually yellowish green 

 when, expanded, but in P. Brittonianum and some of its relatives the 

 sepals are blood-red even before anthesis. Some species are known to be 

 apogamoust and apogamy is to be expected in many others, a circum- 

 stance very probably connected, as in Taraxacum and Hieracium, with 

 polymorphism or close affinity in species as now understood. So far as 

 I know, polyembryony, recorded for Viscum and Arceutliobobium or 

 Razoumofskya,$ has not yet been observed in Phoradendron. 



While the number of internodes composing a flowering spike varies 

 in most species it usually varies within small limits, and its mean appears 

 to be available in most cases in the recognition of a species. Contrasts 

 are afforded by P. Libocedri, P. cuneifolium, P. emarginatum, P. flaves- 

 cens, P. polygynum, etc. Sometimes corresponding to the number of 

 joints, sometimes to their length, and sometimes to both, the length of 

 the spike also presents differences of taxonomic value if used not too 

 arbitrarily, e. g., in P. emarginatum, P. flavescens, P. macrotomum, and 

 P. polygynum. In all of our own species the plants are strictly dioe- 

 cious ; and, as a rule, staminate spikes are longer than pistillate and bear 

 more flowers (PI. 5). This is known to be true also of a number of 

 tropical species, such as P. Wattii; in others, prevailingly if not exclu- 

 sively staminate and pistillate spikes showing something of the same 

 dimorphism occur monoeciously on the same plant. Though usually not 

 too closely applicable as between related species, the number and 



*Honey and pollen are said to be gathered from some species: Richter, Bull. 

 217, Calif. Exper. Sta. Sholl, Bull. 102, Texas Exper. Sta. The staminate flowers 

 of P. villosum are said to have the odor of pond lilies, by Piper and Beattie, Flora 

 of the Northwest Coast, p. 124. 



tC/. York, Bot. Gaz. vol. 56. p. 201. 



\Cf. Weir, Phytopathology, vol. 4. p. 385. 



