14 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



says M. Bommer. The continental form is glaucous. The tree 

 of the wetter coast ranges is green with leaves disposed flat. 

 The two forms shown me were so different that I wondered 

 if there were not some mistake. See above regarding the 

 two forms of Douglas. Says M. Drion, there are two 

 quite distinct forms (i) Abies lasiocarpa { = A. concolor Lowiand), 

 and (2) Abies concolor. Some botanists consider these as different 

 species and others as varieties. There are many intermediate 

 forms between these two types. 



Araucaria imbricata. Doing well both here and at the 

 Groenendaal arboretum. The older trees in the Bois de la 

 Cambre at Brussels give fertile seed ; but few good seeds to the 

 cones. The seeds themselves are equal to South American 

 ones and germinate quite well, says M. Bommer. 



The above notes were taken by me nearly a year before the 

 war broke out. M. Drion had the MS. for some months, and I 

 have since had a very busy time in Australia. Hence some 

 delay in editing these notes. They will have a historical 

 interest if the beautiful forest of Soignes has suffered, like so 

 much else, from the German invasion of Belgium. 



2. The Black Poplars.^ 



{With Five Plates) 

 By Prof. A. Henry. 



About ten years ago, when I began the study of different 

 species for The Trees of Great Britaiti and Ireland, no group 

 seemed so obscure as that of the cultivated poplars. Nowadays 

 one knows that such a group probably comprises not only 

 natural species and varieties, but also sports and hybrids. A 

 natural species is a set of individuals uniform over a large 

 area ; or, in some cases, it consists of two or more geographical 

 varieties which correspond to distinct territories. Such areas 

 of distribution are delimited by conditions of soil, climate, etc. 

 Hybrids, which occur in nature on the boundary line between 



' A part of this article appeared in Gardeners' Chronicle, Iv. pp. 1,46,66 

 (July 1914). We are indebted to the editor for the loan of the blocks 

 of Figs. I, 2, 3, 4, 5, 8 and 9. We are indebted to the Department of 

 Agriculture, Ireland, for the loan of the block of Fig. 10. 



