OENOTHERA NANELLA, 

 HEALTHY AND DISEASED. 



In my cultures of the evening primrose of Lamarck, thie pure 

 and self-fertilized seed yearly produces a certain percentage of 

 mutants, among them dwarfs, Oenothera nanella, the number of 

 which usually amounts to about 1 per cent, of the whole crop. Of 

 late, these dwarfs have been the subject of some discussion, since 

 Zeylstra discovered the presence of a bacterium in their tissues and 

 showed that some of their characters, formerly considered as spe- 

 cific marks, are, in reality, abnormalities caused by this parasite^). 

 From this, some authors have erroneously concluded that the 

 dwarfs are no real mutants, but only diseased individuals of the 

 original type^). 



Zeylstra, however, had pointed out that, under favorable condi- 

 tions, the sideshoots of the dwarfs may become healthy and lose 

 their abnormal characters; but their height remains the same as 

 in the diseased stems. Hence we may assume that, under still more 

 favorable conditions, the main stems themselves might grow up 

 healthy, while still retaining the dwarfish stature. 



About half a century ago, Liebig pointed out that nitrogenous 

 manure is apt to increase the sensitiveness of plants to diseases, 

 whilst phosphate of calcium is one of the best means to diminish 

 this predisposition. Laurent found the same to be true for such 

 diseases as are caused by those common bacteria of the soil, which, 

 under normal conditions, are harmless, but may injure the cultures, 

 whenever the manure is too rich in nitrogenous substances. He 

 studied Bacillus fluorescens putidus and B. coli communis, both of 

 which destroy the cellwalls by means of their enzymes, even before 

 they themselves reach the cells. The bacterium of Oenothera nanella 



i) H. H. Zeylstra Fzn., ^Oenothera nanella de Vries, eine krankhafte 

 Pflanzenart", Biolog. Centralblatt, 191 1, Bd. XXXI, pp. 129 — 139, 



2) Sammelreferat by G. Tischler, Zeitschr. f. ind. Abst, igii, Bd. V, 

 p. 327. 



