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IV. 



THE HISTORY OF THE DUNKELT) HYr.rJD LAliCH, LAR1X 

 EUIiOLEPIS, WITH NOTES ON OTHEl! HYl'-PJI) CONIFERS. 



By AUGUSTINE HENRY, M.A., r.L.S., 



AND 



MAIJGAHET G. FLOOD, B.A. 

 PLATE XT. 



Read Ji-ne 23. Piiblislie'l SEMEMiiER 25, 1919. 



I. — Hybrid Conifers. 



Instance.? of hybridisation between different species of conifers are not of 

 common oceiurence. The fact that species of tlie same genus seldom gi-ow 

 together in the wild state may explain the rarity of hybrids amongst conifers 

 in natural surroundings; but it is difficult to account for their non-appearance 

 in pineta, botanic gardens, and artificial plantations, where allied species 

 often stand in close pro.ximity, and cross-pollination would seem to be 

 inevitable. Most of the recorded cases are confined to the two genera, Abies 

 and Pinus ; and scarcely any addition has been made to the short list^ of 

 hybrid conifers drawn up by Masters in 1901. It is probable, however, that 

 hybridisation in conifers is more frequent than is supposed, and possibly 

 widespread amongst the other genera. Hybrids often escape recognition, and 

 if observed are apt to be classed with so-called " varieties " or " sports." 



As an example of a hybrid conifer whicli has not yet been recognized in 

 books as such, 1 may instance the puzzling^hemlock spruce, Tsuya VaUonmna 

 var. Jeffrei/i, A. Henry.^ This supposed variety is undoubtedly a hybrid 

 between the two wild species, Tmiga Pattoniana and Tsma Albei-tiana, and 

 may now be named Tsuga Jefreyi, A. Henry. 



' In Journ. R. Hort. Soc. xxvi, 97 (1901). 



' In Elwes and Henry, "Trees of Great Britain," ii, 231 (1007). Another name for 

 this tree is Tmqa Mertensiana, var. Jeffrey i, Silva Tarouca, " Unsere Freiland. Xadel- 

 hiilzer," 294 (1913). The hybrid differs from T. Pattoniana in havinj,' green and not 

 bluish foliage, and in the leaves being serrulate and not entire in margin, with a groove 

 on the upper surface continued to the rounded apex. It diBers from T. Albert tana in 

 the r.adial and not pectinate arrangement of the leaves, which, moreover, have broken 

 stomatic lines on the upper surface, absent from the last-named species. 



B.I. A. PROC, VOL. XXSV, SECT. B. [/] 



