1896] A RUST AND LEAF CASTING OF PINE LEAVES 439 
bands parallel to and including, of course, the rows of stomata. 
The color of the diseased part of the leaf and the sori also 
becomes brighter yellow. By the middle of May, if the season 
isa normal one, the sori reach their full development, the color 
at this time being bright orange. As long as the weather is dry 
there is little change in the sori, but at the first rain or fog they 
rupture the cortical tissue, forming long, bright orange red, 
Waxy, or granular elevations, 0.5 to 1™™ high. If the weather 
continues wet the sori retain their bright color, but upon close 
examination they are seen to be overrun with minute cobweb- 
like threads. Lack of rain causes these threads to disappear, 
but for a time at Jeast the sori lose none of their characteristic 
color, size, or shape. Rain or fog will again cause the sori to 
swell, to become granular and waxy, and to show the growth of 
colorless threads, as already described. This alternate drying 
> and breaking out of the sori may continue two and some- 
times three weeks, or it may continue but a few days, the length 
of time varying with climatic conditions and different trees. In 
case of a spell of a week or more of rainy weather the sorus will 
often complete its development and collapse completely as soon 
a the sun comes out for a few hours. Occasional rains, fol- 
lowed by several days of fair weather, prolong the life of the 
Sorus in all cases. 
Under ordinary conditions of humidity the s 
Part complete their development by the middle of June, 
ene month after they first break through. The diseased 
of the leaf at this time assumes a brownish hue and becomes 
More or less shrunken. The sori also turn brown, collapse, = 
te dry up entirely. The tissues below and immediately 
adjoining the diseased areas now begin to turn yellow, this dis- 
‘oloration gradually extending downward until the whole leaf 1s 
volved. 
If both needles are affected by the fungus both SS 
‘multaneously from the normal green to yellow. If, however, 
only one of the needles is affected the change extends from the 
up downward on the affected one and from the base upward ade 
ori for the most 
or about 
portion 
