Vol. XV. No. 3t 



THE AGRICULTURAL NEWS. 



il3 



THE GEyt'S FHORADEXDRON: A Monographic 

 Revision. By William Trelease. Univerdty of Il'inois, 

 1916. Pp. 1-224, pi. 1-245. 



The genus Phoradendron i.s composed of the species of 

 mistletoe occurring in the New World which are of interest 

 to agriculturists principally in respect of their parasitic 

 relations to certain cultivated trees. The genus extends 

 from as far north as Washington to as far south as the 

 mouth of the La Plata, and it is represented through the 

 entire West Indian chain. It is stated that the greater 

 number of tropical species differ from those of the north in 

 being androgynous through the occurrence of a number of 

 staminate flowers on spike points that are otherwise pistillate. 

 The number of species recorded in the different liritish West 

 Indian islands is as follows: — 



Antigua, 2. 



Dominica, 5. 



Grenada, 3. 

 .Jamaica. 12. 



Montserrat, 1. 

 St. Vincent, -J. 



Tobago, 1. 



Trinidad, 6. 



For the convenience of botanists we reproduce the 

 following notice of the work, by O. Stapf. (Kew Bulletin, 

 No. 9 of 1916):— 



'The genus Phoradendron in the New World takes the 

 place of Viicum in the Old. ilost species so resemble the 

 common mistletoe as to be mistaken for it in a winter land- 

 scape; but beneath that great general resemblance is hidden 

 a remarkable differentiation of minor ch<racters often difficult 

 for the inexperienced eye to grasp, but mostly going hand in 

 hand with a definite and frequently narrow geographical 

 distribution. On it is based the author's admission of 

 a great number of species, 240 in all. The number may 

 appear excessive, but the careful scrutiny which he has applied 

 to his .subject and the concordance of bis work and the results 

 obtained by the most careful students in the same field before 

 him, as Eichler and Urban, impress one with confidence in 

 the 'soundness of his limitation of the species. A passage 

 from his introduction (p. 17) may be quoted as characteristic 

 of the stand-point of the author in that respect: "In a mono- 

 graphic assemblage, such as is here offered, no lasting harm 

 can come from the most radical segregation of forms possible 

 on morphologic and geographic considerations, while on the 

 other hand a blending of widely dissociated forms or of such 

 as differ greatly in their extremes though without as yet 

 definable breaks in the series, e.g. P. piperoides, leaves the 

 work to be taken up once more from the very foundation, 

 and with reference to all of the original materials that may 

 have survived.' 



•The introduction (pp. 3-17) gives a short historical 

 summary which implicitly se^ttles the question of the validity 



of the generic name, an analysis of characters, brief notes on 

 the parasitism, the host and enemies of Phoradendron, the 

 orgin of the genus — it is regarded as probably of late Tertiary 

 origin in the New AVorld to which it is confined — and the 

 range of species, the aret of the genus as a whole extending 

 from Washington, Southern Colorado, the mouth of the Ohio 

 and Southern New Jersey to the La Plata in the South. The 

 text, including the description of new species, is in English. 

 The figures cover 237, or nine-tenths of the recognized forms, 

 a very unusual degree of completeness of illustration. They 

 are all reproductions of photographs of natural size, and where 

 possible from type specimens. They will be of great help but 

 they also emphasize the limitations of this process of illus- 

 tration. Many of the figures are no better than outline repro- 

 ductions with all detail lost or blurred. The indices of collec- 

 tors and of occurrence are very full and should be very useful. 

 "The genus is divided into two primary divisions, 

 namely, Boreales and Aequatoriales, which, apart from their 

 geographical areas, are characterized by the absence or 

 presence respectively of cataphyllary scales. Each of these 

 divisions is divided again into subdivisions and some of them 

 again into minor groups. All the sub-divisions and minor 

 groups as well as the species are conveniently keyed. 1. nder 

 each species we find a complete account^ of the synommy, 

 a description, general indication of distribution, and a com- 

 plete list of the .specimens examined.' 



Electricity and Plant Growth —Evidence is 

 accumulating that plants subjected to high tension electricity 

 by means of overhead wires respond by increised vigour and 

 yield. Thus in the experiments carried out by Miss E. C. 

 Dudgeon in 191-5 near Dumfries, oats grown on electrified 

 and non-electrified areas each of H- acres showed a marked 

 response to electrification. The yield of grain in pounds from 

 the electrified area was 1,309, as against 1,003 from the non- 

 electrified control — an increase of grain of 30 per cent. The 

 yield of straw was even more markedly in favour of the 

 electrified plot: 2,476tt)., as compared with 1, 5721b., an 

 increase of 58 per cent. We believe that similar and even 

 more decisive results have been obtained at Dumfries this 

 year, and that electrification again resulted in large increases 

 both of grain and straw. On the contrary, as tho.se who have 

 visited the Pi.H.S. Gardens at Wisley may have observed, 

 similar experiments which have been carried out by the 

 R.H.S., in conjunction with the Imperial College of Science, 

 have not so far yielded results in favour of electriricition. We 

 are informed, however, that these experiments are to be contin- 

 ued during the coming year. If they result in increases of 

 yield of horticultural plants as large as tho.se which appear to 

 be consistently obtained with oats, we may yet live to see 

 the overhead electric, discharge in operation as an adjunct to 

 intensive cultivation. The cost of the current used is but 

 small, although that of the initial installation is by no means 

 inconsiderable. Where cheap current is available, however, 

 the method, if it prove to have a pronounced and positive 

 effect on the crops, should have a bright future before it. 

 (Gardener's Chranide, November 11, 1016.) 



According to infr>rmation received from the Curator of 

 the Botanic Gardens, Dominica, the distribution of plants 

 from the nurseries during November consisted of the following; 

 limes, 9,250 : shade trees, 430 ; budded citrus, 272 ; cacao, 

 25 : grafted mangoes, 7 : miscellaneous, 36. This made 

 a total of 10,020. " 



