18 



ing kept the plants at considerably higher temperatnres (20° to 30° C), 

 and yet having obtained the same results as Dr. Wakker, I am forced 

 to the conclusion that the organism is a rather feeble parasite and that 

 the slowness of its progress in the plant is due to natural causes, tne 

 discussion of which I will undertake later on. 



SERIES 2 (onion). 



On December 13 six shoots of an onion (Allium cepa) were inocu- 

 lated with bright yellow slime from a potato culture (tube 12, Decem- 

 ber 4), by means of numerous needle punctures. 



Result: The plant developed no leaf symptoms, and when the four 

 bulbs (all from one root) were dug and examined in June, 1898, there 

 was no trace of yellow bundles or other indication of disease. 



NATURAL INFECTION OF A DAUGHTER BULB. 



In April, 1897, a diseased bulb was potted and placed in the hot- 

 house. This was the last remaining bulb of those received from 

 Holland the preceding fall, the rest having been cut for study or 

 having fallen to pieces in the dry air of the laboratory, to which they 

 had been exposed for six months. The planted bulb did not sprout 

 for a long time, but finally developed some feeble leaves. No par- 

 ticular attention was given to it during the summer and fall, but in 

 midwinter I noticed that the leaves were dying at the top and were 

 crooked — i. e., came up exclusively from one side of the bulb and 

 curved over toward the other side. In February, 1898, the plant was 

 knocked out of the pot and examined. The bulb which I had planted 

 was completely decayed. All of the leaves were from a small daugh- 

 ter bulb, which was not present, or at least not visible, when the 

 mother bulb was planted. This bulb was one-sided, had only a few 

 leaves, and these were dying at the top. There was no wet rot of the 

 leaves or bulb and externally the bulb was sound. On cutting it open 

 more than forty vascular bundles in the otherwise sound white scales 

 were found to be bright j^ellow, and a careful microscopic examina- 

 tion showed them to be full of the hyacinth germ. These yellow 

 bundles were in eight different scales. That the daughter bulb had 

 contracted the disease from the mother bulb which I planted was 

 evident (1) from the fact that there was no other visible source of 

 infection — i. e., this bulb was planted in good soil, in which hyacinths 

 had never grown and was the only hyacinth in the gi-eenhouse; (2) 

 from the fact that the plateau was the most badly affected part of the 

 bulb; and (3) from the fact that the scales seemed to have been 

 infected from below up, the yellow slime in more than two-thirds of 

 the affected bundles being visible to the naked eye only in the lower 

 half of the scales, whereas in bulbs which became diseased as the 

 result of my leaf infections the upper half of the scales (so far as 

 examined) was always the first to show the symptoms. Probably the 



