The Beach Plum, Viewed from Botanical and 



Economic Aspects. 



(WITH PLATES XX, XXI.) 



By Professor J. M. Macfarlane. 



The publication of Danvin'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 Salvia 

 lyraia, 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 



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