XVII.] EARLIER BLOOM NORTHWARD. 299 



more marked than would appear from the table. The 

 plants from New York seed were by far the largest and 

 most vigorous of any in the test during the month which 

 they remained in the house. This subject was again 

 investigated by two of my students, upon corn, water- 

 melons and kidney beans. The corn gave the most 

 marked results in favor of the northern samples, but 

 there was generally a similar difference in the water- 

 melons and beans, with not one contrary result. 



If the cuttings and seeds of northern latitudes start 

 relatively earlier in spring than those of the south, it is 

 reasonable to expect that spring -flowering trees follow 

 the same law. This subject has not been investigated 

 in this country in connection with coincident tempera- 

 tures, so far as I know, although it is one which prom- 

 ises good results to both the climatologist and the nat- 

 uralist. " Schiibeler states that in the middle latitudes 

 of Europe and North America, flowering is delayed four 

 days for each degree of latitude, but that in higher lati- 

 tudes, according to Berghaus, the retardation is less, — 

 indicating, apparently, that there a given amount of 

 heat had a greater effect."* Probably the easiest way 

 in which we could accurately express the progression of 

 spring, or compare the differences of any two spring 

 climates, is in terms of a physiological constant of 

 the blooming of spring -flowering trees. 



At the present time, the best statement which I can 

 make in illustration of the relative earlier bloom of the 

 north, is to say that most and perhaps all plum trees 

 bloom considerably in advance of the leaves in the 

 southern states, whilst the flowers and leaves are nearly 

 or quite coincident in New York. In other words, with 



•Crozier, Modification of Plants by Climate, 22. 



