590 BACTERIAL DISEASES OF PLANTS 



the above-ground parts of a plant ten months old, 3 feet tall and 

 weighing 399 grams, yielded only 28 grams, or 7 per cent, of 

 water-free substance, most of which, of course, was the woody 

 part. My attention was first called to its watery nature by its 

 marked shriveling when put into alcohol, by its prompt disinte- 

 gration in boiling water containing acidified copper acetate (I 

 could not make a coppered " specimen" of it), and by its exten- 

 sive watery hypoderm. It is not known just where begonias 

 belong in the natural system, but their general appearance and 

 behavior would seem to indicate that they are primitive plants 

 or at least hark back easily to primitive conditions. They are 

 said to be shade-loving plants, but the only one I have seen wild 

 grows on rocks in a tropical sun, and all I have examined under 

 the microscope seem to me to show a xerophytic structure. 

 Probably some grow in one place and some in another. 



15. I should now state the kind of shocks that cause the 

 plant to throw adventive shoots in great numbers. I use the 

 expression "in great numbers" advisedly because the plant is so 

 sensitive that it is always throwing more or less adventive shoots, 

 especially around the stipule-scars, and I am not speaking of its 

 normal behavior but of an abnormal, local and very excessive 

 proliferation, as may be seen from my plates. 



I first experimented with stem- and leaf-woundings. These 

 are effective, but only if made at the proper time, that is, on 

 young tissues. My first experiments made on }/ to % grown 

 leaves and internodes failed, probably because such tissues are 

 too mature. Later, I got many striking results by wounding 

 very immature leaves. My best results were on leaves the 

 blades of which were still red and not over an inch long (the 

 blades of mature green leaves on well-grown plants are 7 to 10 

 inches long). Here, from the margins of needle-pricks and small 

 knife- wounds, where a red callus develops, I obtained dozens and 

 scores of adventitious buds, so many, in fact, that often they 

 were counted with difficulty (see Fig. 447, where only the larger 



by root injury when these internodes were very small, i.e., wrapped in the bud, 

 and the proliferation is ascribed to stimulation due to loss of water. 



3. A branch of No. 1, 1st series, where the proliferation was largely restricted 

 by cork-formation which developed in the stimulated internode. 



