from Botanical and Economic Aspects. 225 



insitiiia or P. dojuestica started our present varieties. I have 

 failed to learn what degree of variability, if any, either of the 

 above species shows in nature, but Dr. Erwin F. Smith 

 informs me that the sand plum of the Northern States varies 

 as does the beach plum. 



It is to be regretted that in the works of Downing and 

 others no exact estimate is given as to fruit and stone weight. 

 The following have been gathered by the writer: Several 

 weighings of the Dawson plum — a variety of damson — gave 

 for fruit weight 4.30 gms., for stone weight .70 gm., so that 

 the ratio here of stone to pulp is about one-sixth, or the same 

 ratio in a cultivated fruit, as already exists in the finer varieties 

 of the beach plum. The " California Tragedy," a reddish- 

 purple fruit, weighed 31 gms., while the stone weighed 1.74, or 

 in ratio as one to eighteen. A market greengage weighed 

 35 gms. and the stone 2.42 gms., or in ratio as one to fourteen 

 and seven-eighths. A specially fine greengage bought in 

 market, and which seemed to answer to Lawrence's gage, 

 weighed 65 gms., the stone 2.25 gms., or in ratio as one to 

 thirty. 



One is immediately impressed by the wide differences shown 

 between pulp and stone in the commoner and finer varieties of 

 cultivated plum. But this is exactly what cultivation has been 

 proved to accomplish for our best fruits. Darwin gives a very 

 pertinent illustration in the English gooseberry. The wild 

 fruit weighs about 120 grains; in 1786 samples were on 

 exhibition which weighed 240 grains ; in 1830 the weight was 

 781 grains, and in 1852 the Hmit of 896 grains was reached. 

 This is fully seven times the weight of the natural fruit. 



If we suppose the wild ancestor of the garden plum tO' 

 have weighed about three grams (since the weight of the cul- 

 tivated Damson already given was 3.30) this would indicate 

 that cultivation has increased it fully twentyfold. But the 

 weight of average beach plums is 2.50 grams, while fine varie- 

 15 



