MR henry's investigation OF ELM SEEDLINGS. 1 89 



species was introduced into France about 1700, and into England 

 some years later. Soon after its introduction into France, a first 

 cross with P. nigra accidentally arose, and this became known 

 in France as P. iiigra helvetica, or " Peuplier Suisse," and in 

 England as the black Italian poplar. As the male form only is 

 known, this tree has been entirely reproduced by cuttings. 



Of the same nature probably also is the cricket-bat willow, 

 though the author has not finished his investigations into its 

 origin. This is only known as a female tree. It originated in 

 Norfolk about 1700, and the author's view is that it is a first cross 

 between Salix alba and S. fragilis, but resembling much more 

 closely the alba parent than the other ; in fact, so closely does it 

 resemble S. alba that it has been considered by most authorities 

 to be a variety of that species, viz., 6". alba var. caerulea. 



As the author remarks, " these experiments seem to show that 

 what are called varieties are often simply Mendelian combinations 

 of two existing species," and he points out that where there is 

 only one species of a genus in a territory or country, as, for 

 example, in the case of the beech or the ash (in which the 

 variations which occur are of a quite different nature), such 

 varieties are unknown, whereas in the case of such genera as 

 Quercus, Betiila, Tilia, etc., the variations are like those of the 

 elm, and where the number of species increases, as in the case 

 of the oaks of southern Europe, the number of " varieties " also 

 increases, sometimes to an alarming extent. 



In concluding this notice, it may be well to quote in full the 

 last two paragraphs of this epoch-making paper : 



"The practical corollary to all these observations seems to me 

 evident. We have instances in the black Italian poplar, in the 

 Huntingdon elm, in the Lucombe oak, probably in the cricket-bat 

 willow, of vigorous first crosses that were produced accidentally, 

 and which are timber trees of considerable value. Why not, 

 then, proceed to make artificially first crosses in other trees, 

 with still more valuable timber ? In the ash and walnut ^ the 

 quality of the wood, owing to its structure, will be improved the 

 faster the tree grows ; and both these trees produce extremely 

 valuable timber. First crosses, of course, can only be re- 



' De Vries, in Plant-Breeding, 174, fig. n (1907), describes a remarkable 

 first-cross walnut which he saw in California. The particulars which he gives 

 about its fastness of growth are so astounding as to seem incredible. I have 

 no doubt, however, of the correctness of his observation.— A. D. R. 



