66 THE JOURNAL OF BOTANY 
uckers are very numerous and the seeds abortive; the other 
ones standing in these respects between these two extremes in 
the order adopted in this paper. It will follow from this that the 
infertility of the seeds in U. pireuloal, which has often been used 
as an argument that this species is non-native in Britain, is seen 
to have a more natural explanation, if it may be assumed that the 
n up maturing its seeds on account of the successful 
output of ite suckers. The recent discovery, kindly communicated 
to me by Messrs. Elwes and Druce, that this species is a Dae 
endemic to arses ines also well be correlated with the 
_ ng of ioe The effort required for sean the Teed 
realized 3 1909 through the fact that aren’ individuals of 
that U. scabra begins to fruit very ote in its Site and rite on ‘al 
its twigs, while U. swrculosa does not begin to fruit until the tree 
is about forty years old, and then hat Se in a usual way only on its 
outermost or highest branches. It is natural to anticipate that, 
after a certain period of Dineliataaicin: this tree will give up pro- 
ducing its samaras altogether 
abit is of great importance in this genus. Being unrecog- 
nizable in the herbarium, this should be carefully noted in the 
field, and recorded on herbarium labels, Fortunately it admits “5 
rip 
n nature that all the species can probably be recognized in 
winter from their habit alone. The chief varieties of habit are as 
follow: 
re sie ce variously curved bole, jong spreading, at length 
drooping limbs, rather slender twigs a 
2. sero straight bole, long eum limbs, less slender 
vegeta 
3. sm oth slender bole, tall or low, ascendi ing, droopin ng 
traight limbs, long, very slender, much divided 
labra 
wigs 
4, Bout bole, branching low down, spreading, at len per 
drooping, pointed limbs, thick, little divided twigs cg 
5. Rough, straight and tall bole, spreading stiff limbs, much 
divided stiff twigs, rounded masses of foliage — surculosa. 
The leaves of each species show a considerable perrioeta aad of 
size and shape on the tree itself, and in well-grown examples; in 
ra the mare the leaves is o lei as a specific 
character, except perhaps in 7 esti vib as a much more 
