146 
THE JOURNAL OF BOTANY 
ALNUS INCANA DC. 
By J. E. Little, M.A. 
As the Grey Alder was distributed in 1922 through both the 
Exchange Clubs, some collected notes upon it may perhaps be of 
interest. “ This alder is not considered to be a native of Britain, and 
has not yet been discovered there in a fossil state : according to 
Alton it was introduced in 1780 ” (Dr. A. W. Hill, in litt. Ap. 3, 
1923) ; ’‘considering the geographical distribution of this plant, it is 
a remarkable fact that it does not occur in Britain ” (Humphrey 
G. Carter, in litt. Mar. 30, 1922). 
The specimens which I distributed through the Clubs were obtained 
from a swamp near ‘The Folly,’ Hitchin, Herts, where A. gluti¬ 
nosa is the dominant tree. My attention was first drawn to it in 
June 1921 by the whitish underside of the leaves of a bush without 
flower or fruit. I took a branch home, and supposed it some kind of 
birch ; but on revisiting the place, I found on another bush a single 
branch with strobiles, and at length arrived at its determination as 
A. incana. In normal years the bog in which the bushes grow is a 
quagmire into which one hesitates to plunge without a definite 
object; but the dry seasons of 1921 and 1922 made it easier to 
explore more thoroughly, and I was ultimately able to count about 
30 patches scattered over the wood, up to 12 ft. high and spreading 
by suckers. They flower some three weeks at least earlier than 
A. glutinosa , and begin to show green leaf before the buds of the 
latter have begun to expand. In the autumn the leaves have fallen 
by the end of September, while the leaves of our alder are still green. 
Though producing flowers and strobiles freely, I have as yet been 
unable to, find matured seed. I submitted a sheet to Dr. Druce, who 
wrote: “The leaves of the Herts A. incana are of a rather different 
texture from those of A. incana as I saw it this summer in Norway. 
Can it be the hybrid A. glutinosa X incana , which we saw there ? ” 
Prof. Jens Holmboe (Bergen Museum) writes, of a Hitchin sheet 
sent to him:—“In some respects it reminds one of A. glutinosa x 
incana f. ambigua (Beck) Callier; but it also comes near A. incana 
f. vulgaris Spach. As favouring the former interpretation, the 
wings of the fruits seem in most cases to be badly developed. In 
other respects it can hardly be distinguished from A. incana. 
According to the opinion of some Scandinavian botanists A. incana 
also includes varieties without distinct fruit-wings. The polymorphous 
form-group A. incana is very difficult, and as yet far from sufficiently 
T 1) * 
known. 
Prebendary R. J. Burdon sent me a sheet of A. incana gathered 
at Romsdal, Norway, Aug. 9, 1922, from which have dropped four 
well-developed seeds. In these 1 can only see a very obscure wing- 
development on one side. The testa is very hairy. The strobiles are 
stalked. The axils of the veins of the leaves are thickly pubescent. 
In an Arnside sheet the strobiles are stalked, but in the Hitchin 
sheets they are mostly though not invariably sessile and glomerate. 
The Arnside bushes have leaves larger than the Romsdal sheet—a 
