1896] A RUST AND LEAF CASTING OF PINE LEAVES 441 
At certain points, which do not seem limited to any partic- 
ular region, the mycelium pushes its way toward the cortical 
region, and between the latter and the mesophyll cells it begins 
to form a sorus or spore bed (figs. zo and rr). This is effected 
by a continued interweaving of the mycelium, which at the same 
time becomes more septate and brown or orange yellow. As 
the spore beds increase in size the cortical region is pushed 
upward, thus giving rise to the pustules already described. With 
increasing age the spore beds become more compact, so that by 
May 10 to 15, or just before they break the tissue, they show, 
beneath the cortical tissue, compact rows of rounded septate 
bodies (jig. rr), the sporophores. 
The sporophores are formed in the following manner: The 
hyphe, which push toward the surface, begin to enlarge at their 
tips (fig. 3 2). Soon:a septum forms just below the swollen 
portion, the result being the formation of a more or less rounded 
cell. By successive abjunction other cells are formed, until the 
sporophores appear in compact rows, as already described. When 
mature and the proper conditions of moisture are present the 
"upper cell of each sporophore gives rise to a mass of gelatinous 
Substance, which has no very definite structure, so far as can be 
‘Scertained from a study of transverse sections (fig: 23). It is 
the sudden development of these gelatinous masses that ruptures 
the cortical tissue, thus bringing the sorus into direct contact 
With air, moisture, and more intense light. In from three to 
four hours after the cortical tissues are ruptured, cylindrical 
bodies, which later develop into teleutospores, begin to shape 
themselves out of the mass of gelatinous material (fig. 14). 
These bodies soon begin to turn yellow and in a short time their 
Walls may be definitely made out. The outer walls of each 
teleutospore consist of an enormously thickened, colorless, 
8elatinous membrane, and it is the massing of these membranes 
that Sives to the young sori the characteristics already i 
t this time it is very difficult to make out the transverse wa s 
‘eparating the teleutospores. Treatment with potash solution 
and with nitric acid, however, brings these out distinctly. 
