140 The American Naturalist. [February, 



ted when the plumule had begun to push through the sheath gave 5 

 smutty plants; finally, 150 infected when the plumule had pushed 

 through the sheath about 1 cm., remained entirely free from smut. 

 Microscopic examinations made a few days after the conidia were 

 sprayed on the seedlings showed that germtube penetrations were very 

 common in that experiment which yielded over 70 per cent of smutty 

 plants, infrequent in those which yielded only a small per cent of 

 smutty plants, and altogether absent in the plants which remained en- 

 tirely free from smut. As in oats, the smut was confined exclusively 

 to the panicle, and the bulk of the infections took place during the 

 earliest stage of germination, the tissues of the growing seedling very 

 soon becoming immune. 



The results with maize were very surprising since they developed 

 three wholly unexpected facts, viz.: (1) The germtubes are capa- 

 ble of penetrating any young rapidly growing part of the plant . 

 (2) The growth of the fungous hypha winch ha> gained entrance 

 into the plant is narrowly localized, the sporebeds developing in 

 situ ; (3) There is no period of rest, the smut beds developing im- 

 mediately, i. e. within two or three weeks of the date of infection. Pre- 

 vious to these experiments it was supposed that corn smut entered the 

 plant when it was a seedling and followed the same law of development 

 as oat smut. In the first series of experiments, which proceeded upon 

 this supposition, the smut conidia were sprayed upon 200 seedlings in 

 the earliest stage of germination ; upon 100 which were a little older ; 

 upon 100 still further advanced; and, finally, upon 100 when the 

 plumule was pushing through the sheath. This work was done in the 

 laboratory and after 14 days the plants were set out in the garden. 

 Contrary to all expectation, very few penetrations could be found even 

 by the most careful microscopic examinations, and these were confined 

 to the root node, none being found upon the sheath, — everywhere over 

 the surface crept the germtubes without being able to enter. These 

 plants were under daily observation and after 10 to 14 days a few 

 lagged behind the rest in growth, and on being pulled up smut pustules 

 were found on the axis a little above the root node. Of the whole 500 

 seedlings, only a few became smutty, viz., 4 per cent in the youngest 

 and 1 to 2 per cent in the older seedlings. In all of them the smut 

 pustules appeared on exactly the spot where the germtubes had entered 

 the plant and within three weeks of the date of infection. All the 

 other plants grew to maturity and remained free from smut. Similar 

 results were obtained from an experiment in which soaked, ungermin- 

 ated kernels of corn were planted in a dunged soil which had been 



