134 : Rhodora [JULY 
toward reduction in the size of the petals. May not the small narrow 
petals of var. micropetala be the oblongifolia character intensified by 
crossing? 
The micropetalous plants of Nantucket have recently (1911) been 
separated from those of the Blue Hills by Bicknell ! under the name 
A. nantucketense. The writer can find in Bicknell’s account little of 
diagnostic value to separate the two forms. Only the following state- 
ment by Bicknell seems distinctive: “I have not been able to convince 
myself that the low and small-flowered Juneberry which finds its home 
on ledges and exposed rocky places is the same as the seemingly very 
local and coastwise Nantucket shrub." The small-flowered Nantucket 
plant, like the small-flowered plants of the Blue Hills, seem more 
reasonably explained as hybrids of A. oblongifolia and A. stolonifera. 
In the series of Mendelian segregates the swamp character may be 
supposed to have been derived from A. oblongifolia, as was also the 
character of the glabrous summit of the ovary. The small narrow 
petals may represent an intensification of the oblongifolia type of 
petal as suggested in case of the Blue Hills form. The calyx lobes of 
A. nantucketense are described as “early reflexed," which suggests 
A. stolonifera rather than A. oblongifolia. In consideration of the 
plausibility of the present interpretation the writer is disposed to 
interpret the Nantucket plant as a Mendelian phase of a hybrid 
between these two common coastal species. 
From the standpoint of geographical distribution the genus Ame- 
lanchier is interesting. It has been plainly shown by various writers, 
and more recently by Fernald in this country, that the chemical 
nature of the soil, within certain limits, is of great importance as an 
influencing factor in distribution.? In addition to the evidence already 
published, two summers in Newfoundland and one in Maine have 
convinced the writer of the importance of this factor in distribution. 
It is with reference to the presence or absence of calcium in the soil 
that the greatest influence on vegetation is seen. Soil free from cal- 
cium apparently soon becomes acid, and the question then is one - 
! Bicknell, Bull. Torr. Bot. Club xxxviii. p. 453. 
? Unger: (title translated) Influence of soil on the distribution of plants as shown in 
the vegetation of North-eastern Tyrol (1836). 
Kerner & Oliver: Nat. Hist. Plants, ii. p. 495. 
Fernald: Rnopoma, ix. p. 149 (1907). 
Hilgard: Soils. 
Rubel: Pflanz. geog. Monog. d. Berninageb.— Engler's Jahrb., xlvii. p. 1-616 
(1911-1912), 
