











454 



DK. F. BUCHANAN WHITE S 



Platk X. 



A diagram to illustrate the various ways in which couipouud hybrids (». *• 



hybrids in whose parentage are included more than two species) may 

 be formed. 



Plate XI. 



A diagram showing the relationship of both Tribes and Species as regards the 



British simple hybrid Willows. The larger circles represent the 

 Tribes, the smaller circles the Species, and the lines connecting the 

 latter indicate that Hybrids between these species have been found in 

 Britain, The circle containing the Tribe Diandree has been divided 

 into four sections to show the altitudinal range of the species, since 

 that limits to some degree the number of hybrids. Section I. i» 

 strictly lowland, the solitary species in it not ascending above 1000 

 feet above sea-level. Section II. includes species which, while 

 most common in the low grounds, yet ascend into the alpine region 

 of Section III. Section III. contains the species which rarely, if ever, 

 descend below 1000 feet, and most frequently occur only at a much 

 greater altitude. Section IV. contains two species which properly 

 belong to Section III., but which occasionally, though very rarely, 

 descend far below the 1000-feet line. The Tribes Pleiandr* and 

 Synandr» include lowland species only. 



INDEX. 



The Tribes are printed in small capitals, the groups in italics, the species an 

 hyorids of Salix in Roman type, and unnamed hybrids are doubly indented. 



d 



Caprca, 377. 



DlANDRjE, 377. 



Fragiles, 362. 

 Sitidulcp, 432. 



Xivea, 421. 



Pentandra, 359. 



Phylitifolice, 39;). 



PLKIANDRiE, 347. 



Purpurea, 447. 

 Rcpentes, 339. 

 Salix 



acuminata, Sm., 413, 420. 



adscenden*. Sm., 392. 

 alba, L„ 370. 



albaxdecipiens, 355. 

 alba Xfragilia, 371. 



alba x pen tandra, 361 



alba xt Hand ra. 354. 

 alupecuruides, Tauaci, 000. 



Salix 



alpestris, And., 441. 

 ambigua, Ehrh., 392. 

 amygdalina, L., 347, 348. 

 angustifolia, Wuff. , 31) 1 . 

 aquatica, Sm., 381, 389. 

 Arbuscula, L., 392, 410. 



Arbuscula, Sm. , 391. 

 Arbuscula xphylici folia. 4 

 Arbuscula X herbacea, 439. 

 Arbuscula xLapponu in, 42 

 Arbuscula X My rsinites, 43 



arenaria, L., 426. 

 atrocinerea, Brot., 380. 

 aurita, L. f 382, 384. 



aurita X Caprea, 387. 



aurita X cinerea, 383. 



aurita X herbacea, 441 . 



aurita X L^pponuin, 429. 







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