Jrom Botanical and Economic Aspects. 225 
znstttiia or P. domestica 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 pulpand 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 limit 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- 
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