114 ‘BOTANICAL GAZETTE [auGusT 
A series of experiments was conducted by Professor H. 
Ness+ to determine certain differences between the growths 
from seed of the same varieties of corn grown at Ithaca, New 
York, and at College station, Texas. Among other things, he 
showed conclusively that in Texas all varieties have a much 
shorter stalk than in New York, which he concluded was due to 
differences in the relative intensity of light, thus verifying pre- 
vious observations. 
In the trans-Pecos country the percentage of sunshiny days 
is nearly as great as in the maximum region of central and 
southern California. Where the Gulf winds prevail, there is a 
relatively high percentage of cloudiness and humidity, which 
reduces the total light effect. But the percentage of sunshiny 
days does not express the real effect of light upon vegetation in 
this region; it is the actual intensity or quantity present at any 
given hour of sunshine. The sun’s rays are almost at the maxi- 
mum intensity during the vegetative season, and their intensity 
is undiminished by atmospheric moisture over most of the area. 
Furthermore, the rock, gravel, chalk, or clay, lacking a green 
covering of vegetation to receive and subdue the light, reflect it 
in blinding intensity. Partly on this account, and partly because 
of lack of air, moisture, and rainfall, there is no densely shading 
vegetation characteristic of the region except in well-watered 
-cafions. The dominant mesquite, huisache, retama, and numer- 
ous other Mimoseae, with their feathery foliage only loosely 
filter the light, but do not interrupt it. The junipers and pines 
of the hills and mountain slopes of the Lower Sonoran zone are 
also relatively shadeless trees, and the scrub oak and the chap- 
arral species generally cast only a thin shade. As a conse- 
quence, the shade loving plants west of the g8th meridian are 
confined to moist crevices or watered cafions and sheltered 
water courses, This feature is emphasized by the absence of 
shade loving pteridophytes, and the general occurrence on the 
exposed rock of eroded areas of sun loving ferns and club 
mosses. 
4 Transactions Tex. Acad. Sci. 2: [part 1]. 1898. 
