April 13, 1912.] 



THE GARDENERS' CHRONICLE. 



235 



allied to the Cornish Elm than to this, I have 

 been obliged to place the variety under U. 

 stricta. Jersey Elms in the Royal Gardens at 

 Kew are labelled " Wheatleyi " ; but I suspect 

 this is a mere nomen, whilst the name sarniensis 

 was given a definite status by Loudon. The tree 

 is perhaps limited to the South of England, 

 and is probably not indigenous. It is com- 

 monly planted, along with Cornish Elms, in the 

 avenues and boulevards of the Channel Islands 



branches descend sharply from the lower main 

 branches. The leaves are large and petioled. 

 and smooth and polished above. 



The tree produces fertile seeds in abundance ; 

 and, judging from Mr. Henry's observations on 

 Elm seedlings, the plant would appear to be a 

 hybrid. No certain evidence of its parentage 

 has been adduced ; but, from its characters, one 

 judges it to be one of the many forms of U. 

 glabra Huds. x nitens Moench. 











Fig. 



105 



ULMUS PLOTII DRUCE, FTOl A PHOTOGRAPH OF A TYPE-SPECIMEN ISSUED 



BY MR. DRUCE, 



(The line represents a sea e of one Inch.) 



and some of the towns, e.g., Southampton and 

 Portsmouth, of the south coast. 



The 



Elm Seedlings. 



It has long been known that the seeds of many 

 Elm trees produced seedlings whose characters 



The 



NITENS M(ENCH— (B) 



Elm (U. glabra Huds. X differ from those of the tree which bore them. 



VEGETA 



Huntingdon Elm, like the preceding 

 * anety, is also, I think, not indigenous ; but it is 

 Being rapidly supplied from nurserv gardens at 

 tne present time. It is more a plant of public 

 Parks and open spaces than of hedgerows ; and it 



never. T w*%k _ _ . ,° _. . 



It is very 



believe, occurs in wood 



a L 11Tl i , . > ~^v,wao xi* wv*/ci2>. it is verv 



2! nt v, aDd nea f, Cambridge. It grows very 



and 



own, and long primary branches winch ascend 

 branrW u P angle in y° un g tre * s > *>*t th * 



tranches become more spreading in aire. Smaller 



Martyn (Gardeners 9 and Botanists' Dictionary, 

 1807) and Loudon (Arboretum, vol. iii, 1838) 

 both emphasised this fact ; and the matter has 

 recently been re-investigated in the light of more 

 modern knowledge by Mr. A. Henry, Reader 

 in Forestry at the University of Cambridge. 



The early interpretation of the phenomenon 

 was that plants which yielded mixed seedlings 



not good soecies : and doubtless 



this 



were not, good species; 

 erroneous view has had a great deal to do with 

 the reduction by botanists of British Elms to two 

 or even to one species. The conclusion is dis- 



credited by the knowledge which has recently 

 been obtained as a result of careful and accurate 



by Mendelian workers. It is now 



riments 



seed 



produce mixed seedlings if it is pollinated either 

 by another "pure line" or by a hybrid. Hence 

 it is now necessary, before it* can be said that a 

 particular plant whose origin is not definitely 

 known is a hybrid, to self -poll mate the plants. 

 and only use the seeds which have been obtained 

 by this means. If such seeds throw mixed 

 seedlings, then it may be regarded as established 

 that the plant which produced them is a hybrid. 

 Even then, however, there is no proof of the 

 parentage of the hybrid. To obtain that it is 

 necessary to produce the hybrid in question by 

 ero pollinating known plants. No account of 

 iy such experiments, so far as I am aware, has 

 ever been published with regard to Elms. 



SUBEROSITY IN ELMS. 



Elms are well known to produce, on occasion, 

 a great excess of corky tissue, and this 4i suber- 

 osity M has been responsible for some of the con- 

 fusion in Elms. Many botanists have nan 1 

 suberous plants U. suberosa or U. campestris 

 var. suberosa; but such names, if founded on the 

 presence of suberous bark alone, should be re- 

 jected as being founded on an abnormality which 

 may occur in any of our Elms, except the \Y\eh 

 Elm (U. glabra Huds.). The different Kims pro- 

 duce tuberosity in different degrees : it is com- 

 mon, for example, in the Dutch Elm (x U. 

 hollandica), and rare in the Huntingdon Elm 

 (X U. vegeta). The suberosity is commonest on 

 the young branches produced from adventitious 

 buds low down on the trunk, and on suckers. The 

 cause of this suberosity is a matter for invest a- 

 tion by the plant pathologist rather than the 

 systematise It is interesting that all our Elms 

 l/hfch produce suberous bark also have suckers. 



Rough-leaved and Smooth-leaved Elms. 



-Another matter which has caused confusion is 

 the smoothness or roughness of the upper surface 

 < t leaves of Elms. In the Wych Elm (U. glabra 

 Huds.) and the English Elm (U. campestris L.) 

 all the leaves are invariably rough above ; but the 

 remaining Elms are usually described as having 

 leaves which are smooth above. This, however, 

 only applies to leaves which are produced in 

 spring on young branchlets of the main branches. 

 These, in the key which follows, are termed 

 normal leaves. It does not apply to leaves 

 farmed on suckers, or on twigs produced from 

 adventitious buds low down on the trunk, or on 

 coppiced or cropped shoots, or on seedlings, or 

 even on the new shoots produced in summer on 

 the main branches : all these leaves are invari- 

 ably rough above. This, I believe, has never been 

 pointed out before ; and, in assessing the value 

 of old descriptions, it is sometimes necessary to 

 reject all references to the smoothness or rough- 

 ness of Elm leaves. It is very interesting, too, 

 that the leaves of the summer shoots fall before 

 the normal leaves, often a week or ten days before 



them. 



Size of Elm Leaves. 



Finally, the size of Elm leaves has led to con- 

 fusion through not allowing for the variability in 

 each species or variety or hybrid. Of course, 

 on every shoot the size of Elm leaves varies 

 enormously (cf. fig. 105); and, in the following 

 key, descriptions of Elm leaves refer only to the 

 terminal leaves of each branch (unless otherwise 

 stated). In addition to that, however, it is not 

 unusual to find in each species some individuals 

 which produce much smaller leaves than the rest. 

 Very often the small-leaved examples are old or 

 decrepit trees; but this is not always the case. 

 However, by allowing for the kind of variation 

 pointed out in this and the previous paragraph/ 

 it is possible to identify any British Elm by its 

 normal leaves alone ; and I have no doubt, if 

 proper attention were paid to sucker-leaves, &c, 

 Elms could also be identified by these. It is, 



