17 



These bulbs were planted close together in a shallow pot of sandy 

 earth, only the lower half of each bulb being buried. The plants 

 were on a bench in a greenhouse, where there was an abundance of 

 light and air and where they received water from time to time as 

 required. The external symptoms were so slight and progressed so 

 slowly that no record was kept after March 22. The plants were, 

 however, under almost daily observation during April and May. 

 The}^ made a vigorous growth for two months or more after flowering 

 time, but as the warm weather of summer came on the leaves gradu- 

 ally dried out and died from the top down, and, with the exception of 

 the bases, were pretty uniformly shriveled by the middle of June. 

 This shriveling was not, however, the result of the disease. In fact, 

 so little increase of symptoms was observed in April and Maj^ that 

 when the bulbs were cut open (June 23) it was with no expectation 

 that any diseased places would be found. That some of the leaf 

 inoculations did dry out and fail after starting was evident, but enoiigh 

 succeeded to place the success of the experiment beyond doubt, one 

 or more bundles in the bulb scales of each one of the 8 different 

 plants being yellow, broken down, and full of bacteria (see PI. I, fig. 1). 



None of these plants became wet-rotten or bad-smelling as a result 

 of the bacterial infection, the symptoms being wholly unlike those 

 obtained by Dr. Heinz with his Bacillus hyacinthi-septiciis. So far 

 as observed the diseased plants had no odor whatever; certainlj^ no 

 pronounced odor. No mycelium was present in any of these yellow, 

 broken-down bundles, or in any of the bulb scales, and in most cases 

 no micro-organism of any sort was present except the one which had 

 been introduced into the leaves (and scape) in the preceding Febru- 

 ary; i. e., more than four months before and at a distance of from 15 

 to 25 cm. from the bulbs. No animal parasites were observed. 



Nearly all the scales of these eight bulbs were still entirely sound, 

 but from the condition of the plateau, when the germs had penetrated 

 that far, it was evident that a general infection of the scales and a 

 more or less complete destruction of the bulbs would have been only 

 a matter of time. Even in the attacked scales the greater part of the 

 tissue was still sound. 



Previous to making these inoculations I was inclined to attribute 

 the slow progr(!ss of the disease in Dr. Wakker's inoculated plants to 

 the low temperature at which his plants were kejit, or else to his hav- 

 ing used cultures containing very few living germs. ^ Having myself 

 inoculated from a culture in prime condition for experimental pur- 

 poses (i. e., swarming with motile rods), having in nearly one-half the 

 cases inserted great numbers (that is, thousands) of the germs, hav- 



' From my critical review, published in 1896, it will be seen that even then I was 

 inclined to regard Dr. Wakker's statements respecting pathogenesis as substan- 

 tially correct, and my subseciueut studies have fully contirnied this view. 

 8970— No. 20—00 2 



