Botany and Zoology. 75 
a 
maize may be regarded as a tropical plant, inured to northern 
latitudes only by the development of precocious and dwarf varie- 
ties, and, requiring a longer season and a greater sum of heat 
Schiibeler is said to have shown that biennials and perennials under 
these conditions lay up a greater store of nutritive matter. 
Flahault has carried on a series of comparative experiments in 
this regard, simultaneously conducted at Upsal is. The 
mean temperature of the summer months differs only slightly, and 
the rain-fall is nearly the same in the two places. But the mean 
length of the day, between the 15th of May and the 30th of July 
is 17 hours 49 minutes at sal; at Paris, 15 hours and 38 
minutes. These experiments are detailed at length in his paper 
in Ann. Sci. Nat. (Bot.) 6th Ser., ix, p. 159, ete., March, 1880,—to 
be concluded in the April number. The results, so far, favor the 
0 it loses this precocity in a few generations, and the 
seeds gradually diminish to the former size and weight. Plants 
raised from seeds ripened in a high northern locality are hardier 
mere diurnal dimin 
has shown that electrically illuminated plants require no diurn 
rest, but can be forced on, at least for a considerable time, and 
