624 BACTERIAL DISEASES OF PLANTS 



Johannsen makes light of the work of Dubois, as does also 

 Overtoil. Johannsen objects that the figure which Dubois 

 shows (that of an Echeveria exposed to chloroform and 

 exuding drops of water from all of its leaves) is the figure of a 

 dead plant, and this may well be, but clearly there must be all 

 stages in the exudation of cell-water from its mere beginnings in 

 the live plant to its end, when not only the intercellular spaces 

 and the sub-stomatal chambers are filled with the exuded sap, 

 but also a sufficient quantity has exuded to appear on the sur- 

 face in the form of tiny drops and to have exhausted the cells 

 beyond recovery. In fact, Overton admits that there is loss 

 of water from narcotized muscle and that Dubois is not wholly 

 wrong. Recently I have observed all stages of dehydration in 

 chloroformed cabbages. If the anesthetization is moderate 

 there is only a spotting of the leaves (innumerable tiny spots, 

 water-soaked or darker green by reflected light and translucent 

 by transmitted light) without surface exudate. If the chloro- 

 forming is continued longer, the change of color overspreads 

 the whole leaf, and, if it is an undeveloped leaf with small inter- 

 cellular spaces, there is an exudate of clear fluid from hundreds 

 of stomata mostly to the under surface of the leaf, but, if it is 

 an older leaf, the large amount of intercellular space is sufficient 

 to accommodate the exuded water and it seldom appears on 

 the surface. What becomes of such leaves depends on how far 

 the dehydration is pushed. If the experiment is stopped before 

 the exudate or spotting appears the leaves recover, if pushed 

 until exudate appears on their surface I have not seen them 

 recover. 



Temporary loss of function on the part of the protoplasmic 

 cell membrane whether brought about by chilling, by hot water, 

 by anesthetics, by acids, or by alkalies would lead, I believe, to 

 the same set of phenomena; viz., loss of water, disturbed respira- 

 tion, more or less oxygen-hunger, and compensatory cell-division 

 with movement of water, sugar and other foods back into the 

 growing point. Once the dormancy is overcome buds will 

 continue to grow if placed under growing conditions. I believe, 

 therefore, that we have in these common forcing methods added 

 evidence that the phyllomania in this begonia must be due to 



