73 



BEIJERINCK had not heard of the chimeras, which H. WINKLER had 

 shortly before obtained from the bittersweet and the tomato, and 

 w r hich were to lead the Adami-problem into a completely new trend. 



BEIJERINCK considered Cytisus Adami as a hybrid between the 

 above-mentioned Cytisus species obtained by grafting, of the kind 

 which H. WINKLER later called "Burdo". He therefore called Cytisus 

 A dami a graft-bastard. It is self-evident that for this reason the con- 

 clusions drawn by BEIJERINCK on the formation of bud variants cannot 

 be maintained in the light of the more recent knowledge on the 

 nature of the "Propfhybride". This does not preclude the fact that a 

 great number of observations and remarks occur in BEIJERINCK'S 

 publications which have retained full significance. It is therefore 

 remarkable that they are quoted only occasionally, and that, for 

 example, in an otherwise very complete survey of the problem by N. 

 P. KRENKE, entitled "Wundkompensation, Transplantation und 

 Chimaren bei Pflanzen" ') they are not mentioned. From KRENKE'S 

 survey it appears that the problem is not yet completely solved, 

 notwithstanding the great deal of work clone on it since WINKLER'S 

 publications of 1907 and 1908. BEIJERINCK'S careful observations 

 may certainly contribute still towards the solution. 



To support this claim I mention here only one of his observations. 

 BEIJERINCK determined that the leaves of Cytisus purpureus show a 

 reaction which he had described for a few other leaves in 1900 (in a 

 treatise on the formation of indigo 2 )), and to which he had given the 

 name "necrobiose reaction". If one heats the top of a leaf of C. 

 purpureus for a short time above a flame, practically at once a black 

 band appears at some distance from that top. This must be ascribed 

 to the reaction of enzymes developed from the dying protoplasm (the 

 enzymes are killed at the top) on the constituents of the sap. The 

 same experiment with a leaf of C. laburnum does not produce this re- 

 action. A leaf of C. Adami shows in the necrobiotic region only a 

 brown coloration which moreover occurs not until a few minutes have 

 passed. BEIJERINCK states that it is possible with this reaction to 

 distinguish small leaves of C. purpureus, only a few centimeters long, 

 or still smaller, from those of C. laburnum and C. Adami. 



It is very probable that this reaction could be converted into a micro- 

 scopical one wherewith the nature of the cell-layers of the bastard may 

 be determined, and that a solution will be reached, in this manner of 

 questions which are still waiting to be answered. We call to mind here 

 that LANGE 3) and KRENKE (vide pp. 639 and 640 of his above- 

 cited work), in their study of periclinal chimerae, made use of the 

 difference in the ability of the cells of the two species to take up dyes. 



1) Berlin 1933. 



2 ) On the Formation of Indigo from the Woad (Isatis tinctoria), Proceedings of the 

 Section of Sciences, Kon. Akad. van Wetensch., Amsterdam2, 120-129, 1899 (Verza- 

 melde Geschriften 3, 329-336), and: Further researches on the Formation of Indigo 

 from the Woad (Isatis tinctoria), Ibid. 3, 101-116, 1900 ( Verzamelde Geschriften 4, 1-12). 



3 ) F. LANGE, Vergleichende Untersuchungen uber die Blattentwicklung einiger 

 Solanum-Chimaren und ihrer Elterarten, Planta 3, 181-281, 1927. 



