The Beach Plum, Viewed from Botanical and 
Economic Aspects. 
(WITH PLATES XX, XXI.) 
By ProFessor J. M. MAcFARLANE. 
The publication of Darwin’s “Animals and Plants Under 
Domestication’ made us familiar with a large body of facts 
bearing on the variations of plants under man’s selective 
influence. It has been frequently objected, that the numerous 
cases of variability there quoted, are of little value as guides 
to the interpretation of natural phenomena, since they were 
produced under the guiding agency of man, and could not be 
paralleled in nature. Recent studies have in part removed 
such objection, but every contribution to the subject of varia- 
tion in the wild state has a special value. The subjoined 
observations are brought together from study of a wild plant 
that shows marked variability along several lines. 
It has been frequently accepted—and for good reasons— 
that marked variations are primarily due to the combined 
action of such environmental agents as light, heat, moisture, 
soil surroundings, or winds acting to different degrees in 
different localities. The writer gathered plants of Salva 
lyrata, some years ago, south of Savannah, Ga., that were so 
vigorous in growth, so abundantly bloomed, so large and 
richly colored in the corolla and even leaves, as to suggest its 
being a different species from our Northern type. Careful 
study showed it to be an improved variety of the species, 
called forth probably by the warmer, brighter climate of that 
region. 
But when plants that are specifically identical exhibit marked 
variation in the same geographic and climatic centers, and 
(216) 
