June 23, 1916] 



SCIENCE 



883 



ism. I certainly have abundant material 

 of the end terms (Numbers 1 and 4), and 

 enough of 2 and 3 to convince myself, if 

 not others. 



The ' ' further evidence ' ' alluded to in the 

 title of this paper relates more especially to 

 the embryomas and consists of the dis- 

 covery of an entirely new type of plant 

 tumor due to the crown-gall organism, in 

 which tumor there are not only ordinary 

 cancerous cells of the common crown-gall 

 type but also entire young shoots or 

 jumbled and fused fragments of leafy 

 shoots and of other young organs, thus ma- 

 king the tumor correspond to the highest 

 type of animal cancer, in which in addition 

 to the blastomous element there are frag- 

 ments of various fetal tissues, sometimes 

 representing many organs of the body. 

 This is, I believe, the first time this type of 

 tumor has been produced experimentally, 

 and it has been done with the bacterial 

 organism cultured from an ordinary rough 

 crown gall of the simpler, well-known type. 

 It was first done by inoculating the leaf 

 axils of growing plants, i. e., the vicinity 

 of dormant buds, in other words, centers 

 containing totipotent cells. Some of these 

 strange tumors have produced daughter 

 tumors in other parts of the stem and in 

 leaves and, as in the embryonal teratomata 

 in man, a portion of these secondary tumors 

 have the full structure of the primary 

 tumor. 



I have also produced these teratoid tu- 

 mors in parts of plants where no totipotent 

 cells are known to exist, but only young 

 plastic cells normal to the parts and hitherto 

 supposed to be able to produce only one kind 

 of organ. This will be plainer if I say that 

 by needle pricks introducing the bacteria 

 locally I can now produce atypical teratoid 

 tumors in internodes and in the middle of 

 leaves, an astonishing discovery, and one 

 bound, I believe, to revolutionize our views 



as to the origin of these tumors in man. I 

 do not here deny that totipotent cells, 

 hitherto unsuspected, occur in the places I 

 have inoculated, indeed they must so occur, 

 but I only cast doubt on their abnormal 

 occurrence in such places, i. e., as the result 

 of early embryonic dislocations. 



The belief that I have also produced 

 "mixed tumors," that is, tumors containing 

 distinct types of tumor cells originating 

 from different layers of the plant, rests on 

 stained sections of tumors from several 

 different kinds of plants. The evidence 

 here is not as complete as in the case of the 

 embryonal teratoma, and I am still experi- 

 menting. What I think I have in one part 

 of the tumor is sarcoma originating from 

 the deeper connective tissue layers and in 

 another part of the tumor carcinoma de- 

 rived from the skin and glands of the plant. 

 However this may be, it is now beyond 

 question that two very distinct types of 

 plant tumor (sarcoma and embryonal tera- 

 toma) corresponding to similar types in 

 man, as nearly as plant tissues are able, 

 can now be produced by bacterial inocula- 

 tions, using the same organism. To get one 

 type of tumor I inoculate one set of tissues, 

 and to get the other type, another set of 

 tissues. 



Coming to the details of my newer 

 studies, I shall first take up the question of 

 the possible existence of carcinoma in 

 plants, the slides I shall show you being 

 from photomicrographs of what I con- 

 sider to be "mixed tumors." All are due 

 to pure-culture inoculations, but they show 

 a diverse internal structure suggestive of 

 a mixture of epithelioma (skin cancer) and 

 sarcoma (connective tissue cancer). There 

 is still, perhaps, some doubt as to the inter- 

 pretation of these facts, so that I speak only 

 with reserve. 



The first slide I show you is from a tera- 

 toma on the common Pelargonium or house 



