1893.] PUBLIC DOCUMENT — No. 33. 215 



exposed. The rate of growth of the stalks maybe indicated 

 by the fact that two which were five millimeters long June 

 28 (fig. 3) had become nine millimeters long July 8, ten 

 days later. Two months after the beginning of the culture 

 several sclerotia showed from one to four stalks each, some 

 of them well developed. These stalks are bundles of nearly 

 parallel threads, arising from the inner tissue of the sclero- 

 tium and bursting through the rind. They are at first white, 

 except for a short distance above their bases, and their sides 

 are clothed by the short and delicate free ends of some of the 

 outer threads. If they assume an erect position from the 

 first, their basal portions are only slightly dark colored 

 (figs. 3 and 7) ; but if, as often happens, they grow for a 

 time beneath the surface of the sand or soil, these portions 

 may have hardened and blackened surfaces (fig. 5). These 

 stalks, or their aerial portions, are very sensitive to light. 

 In cultures before a window the young stalks grew from the 

 first strongly toward the window. When the culture cham- 

 ber was turned through 180°, so as to make them point away 

 from the window, they very i)romptly res[)onded to the stimu- 

 lus of the light, and in a single day showed strong hclio- 

 tropic curvature. In two or at most three days they had l)ent 

 sharply upon themselves, and were again directing their tips 

 obliquely toward the light, in response to the combined in- 

 fluences of negative geotropism and positive heliotropism. 

 By the time a stalk reaches a length of al)out five milli- 

 meters above the surface of the sclerotium or of the soil, a 

 conical depression begins to appear in its upper end (fig. 7). 

 This depression arises and increases in size by greater growth 

 at the circumference than at the centre of the stalk, and the 

 final result is a shallow cup crowning the stalk. Some idea 

 of the rate of growth of these cups may be gained by com- 

 paring the stages a and b in figs. 4 and 5, in each of which 

 the condition shown at b represents the gain in four days 

 over a. Under favorable conditions the cups may reach a 

 diameter of as much as eight millimeters, and they have been 

 been even larger. Ordinarily, when they become larger 

 they are also much flattened, having often the form of disks, 

 with only slight depressions at their centres. When mature, 



