552 JOUENAL OF THE KOYAL HORTICULTURAL SOCIETY. 



on the same substratum the difficulty becomes even greater. Moreover, 

 some species have an extraordinarily local distribution, since a single 

 species may be confined to one particular and isolated area " where it 

 exists as it were on an island cut off from its nearest allies." 



Mr. Hill believes that the most satisfactory explanation of these facts 

 is that the many specific forms have arisen as chance variations, sports, or 

 mutations. Such mutations may either have remained where they arose 

 or they may have gradually spread, and as they spread they may themelves 

 have again varied and thus given rise to new and slightly different races, 

 which produced in this manner a chain of allied forms distributed over a 

 fairly extended area. Certain forms may perhaps have remained stable for 

 long periods and by the intercalation of other unrelated species, and 

 possibly by the dying out of those most nearly related to them, these 

 forms may have come to occupy isolated positions. — B. B. 



Oenothera Hybrids, Cytology of (Bot. Gas. vol. xlviii., No. 3, 

 pp. 179-199, September 1909 ; with 3 plates).— Mr. Eeginald Ruggles 

 Gates finds that the hybrids of 0. lata and 0. gigas have twenty-one 

 chromosomes in the somatic cells of which fourteen are of paternal origin 

 (0. gigas) and seven maternal (0. lata). (In one individual there were 

 only twenty chromosomes). The numbes present in any individual 

 is always the sum of the chromosomes in the germ cells from which 

 that individual is formed. At the time of reduction, half the germ cells 

 receive ten and half eleven chromosomes, but nine or twelve chromosomes 

 are occasionally found. — 67. F. S.-E. 



Onion, The Wild (U.S.A. Dep. Agr., Bur. PI. Incl. ; Nov. 1908).— 

 Hints on the best means of extirpating the Wild Onion (Allium vineale). 

 Besides its wide-spread dissemination by means of aerial bulbils this 

 weed possesses one peculiarity which makes it more than usually trouble- 

 some. Each bulb divides into a bunch of bulbs, one of which, covered by 

 a soft skin, starts growing at once, while the other smaller ones, encased in 

 a horny covering, remain in the ground some months before they sprout. 

 It is therefore necessary to resort to two distinct operations in order to 

 destroy the pest thoroughly. — M. L. H. 



Opuntia rubricata. By N. E. Brown (Bot. Mag. tab. 8290).— Nat. 

 ord. Cactaceae ; tribe Opuntieae. Mexico and S.W. United States. 

 Shrub, 3-7 feet high, or tree, 15 feet. Flowers 2-3 inches across, bright 

 purple. — G. H. 



Orchard Fertilization. By J. P. Stewart (U.S. A. Exp. St., Penn- 

 sylvania, Bull. 91 ; April 1909). — We have few accurate data upon which 

 an exact system of orchard fertilization can be based, and this does not 

 add much to our definite knowledge, for, after quoting the evidence 

 afforded by three well known long-time experiments (among them 

 Woburn), only one of which showed decided beneficial results from ferti- 

 lizers of any kind, details are given of an elaborate system of experiments 

 which have been in operation in this State since 1907, the results of which 

 should be valuable in years to come. There is one outstanding feature : 

 the results of the application of soluble nitrogen coincide with those of 



