i8o Journal of Agricultural Research voi. vi. no. 4 



or function as long as the stimulus lasts. These inoculations (on the 

 Paris daisy) have brought out another interesting fact. As the tendency 

 of young fundamental tissue (the growing point) is to form a stele in its 

 center, so when the mature tissues of the stem cortex are brought under 

 the new stimulus and begin to proliferate, in the manner of embry- 

 onic tissues, primitive but imperfect stele-forming tendencies are devel- 

 oped in the tumor. I have not seen an actual shoot produced by such 

 a tumor; but sieve tubes and trachei are formed in it (out of descend- 

 ants of cortex cells, be it remembered); and cross sections of some of 

 these small tumors show that these stelar elements have a tendency to 

 be arranged in the form of a closed structure (primitive stele), although 

 often this is not pronounced. These superficial tumors have no connec- 

 tion with the xylem or phloem of the true stele, for in no case did the 

 needle punctures enter as far as the phloem, much less the cambium, and 

 serial sections show clearly that all of their structures (blastomous cells, 

 trachei, and sieve tubes) have been developed wholly, out of cortex cells 

 (probably cortex mother cells). After a few weeks such shallow timiors 

 cease to grow, or develop very slowly, owing to imperfect nutrition (lack 

 of all connection with the xylem and phloem of the plant). 



Third, when the crowngall organism (hop strain) is inoculated into 

 the leaf axils of young growing plants (species of Pelargonium, Nicotiana, 

 Lycopersicum, Citrus, Ricinus, etc.) the buds of which are in a dormant 

 state and which under ordinary conditions will continue dormant — 

 namely, unless the top of the plant is removed — a new type of tumor 

 develops, one hitherto not seen in crowngall. Inoculating in this way 

 I have obtained tumors covered all over with diminutive, abortive leafy 

 shoots, or flower shoots, if flower anlage have been disturbed. The 

 shoots may be variously twisted, fused, and fasciated, as in the common 

 house geranium {Pelargonium spp.) shown in Plate XVIII. This appar- 

 ently is what happens : The growth of the tumor distorts the tissues, tear- 

 ing the anlage into small fragments which are variously distributed and 

 develop on or in the tumor into organs of a size proportional to the size 

 of the included fragment — here as part of an ovary or anther, there as 

 a shoot. These pathological shoots live but a short time and are quite 

 unable to carry on the normal activities of the plant when the other 

 leaves are removed. I have believed for a long time that fasciation 

 must be due to a bacterial infection ; but this is, I believe, the first time 

 that anyone has obtained it by means of a pure-culture inoculation. 



The results obtained by inoculating the upper leaf axils of young 

 growing plants of the castor-oil plant {Ricinus communis) are prompt 

 and quite as striking (PI. XIX). 



On tobacco plants {Nicotiana tabacum) these teratoid tumors, devel- 

 oped in leaf axils <Pls. XX and XXII), have also produced secondary 

 tumors repeating the structure of the parent tumor. Such tumors have 

 been obtained both in stems and leaves, especially when inoculations were 



