638 Journal of Agricultural Research voi. xv, No. 12 



57, B). They usually touch, but do not crowd one another. Adjacent 

 to the points where one spore abuts on its neighbors there may be con- 

 siderable space. Cross sections of the columns (PI. 52, E) show that 

 the spores are only very slightly angular as a result of mutual pressure. 

 Although they vary widely, normal mature teliospores average approxi- 

 mately 16 by 42 /i, with a wall about 2 ix thick. They are uninucleate, 

 as a result of the fusion of the two nuclei which are normally present 

 in the young teliospores. The mature telial column is an aggregation of 

 a number of vertical rows of mature teliospores (PI. 52, C). The length 

 and diameter of the columns vary greatly ; they may attain a length of 

 2 mm. and an average width of approximately 100 ju. They are usually 

 curved or semispiraled, a result apparently of unequal development 

 of the spores of some of the rows. They vary from almost spherical 

 to irregular ovoid or elliptical in cross sections. Occasionally abortive, 

 nondeveloped spores are scattered throughout the length of tlfe column 

 (PI. 52, C, D). Other abnormalities will be discussed briefly later. 



GERMINATION OF TELIOSPORES AND PRODUCTION OF SPORIDIA 



All of the spores in the telial column may germinate in situ (PI. 56, C). 

 The exospore pushes out at some point in the form of a rounded papilla, 

 which ruptures and allows the extrusion of a stout germ tube — the 

 young basidium or promycelium (PI. 57, D). This reaches its full size 

 in a few hours and then becomes divided into five cells (PI. 57, R) 

 From each of the four upper cells arises a stout sterigma, on the tip of 

 which the sporidium swells to its full size (PI. 57, S-V). When abstricted, 

 the sporidium is almost exactly spherical, measuring approximately 8 to 

 10 // in diameter. At one point on the thin wall is a tiny papilla-like 

 swelling, which marks the point of attachment to the sterigma (PI. 57, 

 AA, HE, GG). 



The germ tubes from the spores in the middle of the column work 

 their way out through the intersporal spaces and then develop in the 

 manner described above. If the teliospores germinate under water, 

 the germ tube lengthens out into a narrowly spiraled or twisted hypha; 

 in other words, promycelia do not develop unless they have access to the 

 air. The color of the germinating column, a very pale pink, gives a 

 distinctly characteristic appearance to the fungus at this stage. 



GERMINATION OF SPORIDIA 



The sporidia germinate in artificial culture by sprouting relatively stout 

 germ tubes (PI. 57, X, Y, Z, BB) which probably continue growth in the 

 normal fashion under favorable environment. In many cases, however, 

 the short germ tube swells at its tip on reaching a length of several mi- 

 crons and the swelling becomes a secondary sporidium, apparently ex- 

 actly similar to the primary one (PI. 57, CC, DD). Sappin-TroufiFy (51) 

 has figured the same phenomenon for the sporidia of Cronartium flaccidum 



