KINDS OF LIGHT. 7 
TABLE 1.—Light intensity of direct sunlight and of diffused light at various 
latitudes. 
Chemical inten- 
sity— 
Places. ILI OC es) $$$ LE 
Ofsun- | Of sky- 
light. light 
° 
PO] Ge Se ER NSE AS 1 DNV ORE RUE AAR BEE ASN AG Be IE EG 8 ee 90 0 20 20 
ING lyvpill Vi Learn see Se ACROSS OVERS a nce Nepean ays oc syrah 75 12 106 118 
EV eyilajaivallc lice learn Geet ee a ee UE ELE cea I SR PUES Cee ie Siege ener 64 60 150 210 
Sie IPSS oles INI CBC ean ea ceseaancaoauadeas Ee at Mn araly 60 89 164 253 
Mian cles Gere tei gi) em eae eat ieee ate ia ea Le ABIES ented 53 145 182 327 
Tei Pel er ess Gere Gia eect ie MN Ne VER eg sha a 49 182 191 373 
INEN OSS NPN Neer ee ei crc ain i meee ia iie pp ein munya aul eed teat Al 266 206 472 
Cano NE ory Gace aie 5 Oe Seer Wace sei ao nN ape abe me yyy les ep Teta 30 364 217 581 
1SKoioa Oe a ba DENS GG SOMME Nuno e es Ue cuia a men Hel Menard esas ne ey ay 19 | © 438 223 661 
Sam Josey Costar ica eee see ey eee Sy sy aieee see cy egoysl cael ese 10 475 226 701 
Qari GOR Cura COT See aN de EVN eee RL ater r vay Le ate 0 489 227 716 
1 From Handbook of Climatology, by Dr. Julius Hann, p. 116. 
Diffused light decreases with increase in altitude; direct sunlight, 
on the contrary, increases. , 
OVERHEAD, SIDE, AND REFLECTED LIGHT. 
Besides direct and diffused hght, ight may be distinguished in 
accordance with the direction from which it comes and the effect it 
has upon the different parts of the crown. The light which reaches 
the crowns of trees 
from above is called a 
overhead light. (Fig. 
1,a.) This determines 
. \ 
the arrangement of 3 Se LD \ | 
leaves on the shoots, 
their position in rela- | ye = 
tion to the sun, and : _ | oe j 
the arrangement of FG a / 
the) oranches. Tit 1s ‘ bee ff 
the strongest light, ee ; 
whether it consists of @ ie ge 
either direct or dif- eee 
fused light alone or | 
both together. In 
the case of dominant 
Oy yy 
5 a Say yf, yy 
trees it equals the to- a | Ta ot) 
a S at cae NY Ni ») raat ate pend SY een 5 
. oN » Sa Sas aN wt UG, one 
= NWN 5 si SUMAN MC 
tal daylight. NS MG rise 
se S Ze oa ae 
The light which oo Gale 
Fic. 1.—Overhead light (a); side light (0); reflected side 
reaches the UO aS of light (c) ; reflected ground light, from a water surface (d@). 
trees from the side 
is called side hight. (Fig. 1, 6.) It stimulates the development of 
buds on the lateral branches and is responsible for the development 
of the branches facing an opening in the forest. 
90431°—Bull. 92—11 
wv! 
3) ~ 
et 
