SUPPLEMENT 113 



I. 39, after versa, read This is just as apparent in plants which flower once 

 only as in those which do so often, e. g. our native trees. In the case of the 

 latter we see the flowers produced on the feebly-developed short shoots, and all 

 factors which aid in inducing the formation of short shoots also promote flower- 

 ing, while, conversely, the transformation of a short into a long shoot deprives 

 such a shoot of its capacity for blooming (comp. VOCHTING, 1884). 



II. 45-8, for It is always . . . very suggestive, read The question now 

 before us is whether the external factors operate directly on the growing point 

 or through other parts, so as to cause this growing point to become a flowering 

 axis. KLEBS (1904, 1908) has endeavoured to refer to one general principle 

 the effects of external factors of various types which induce flowering. He 

 points out that flowering and vegetative growth take place under the same 

 external conditions, and that only quantitative changes in these factors decide 

 what the result shall be ; new stimuli acting specially on flower formation need 

 not affect the plant, but only a variation in degree of factors already operating. 

 KLEBS regards the most important of these changes to be an increase in the 

 organic substance ; the absolute amount need certainly not be increased. A 

 seedling beetroot arising from a dense sowing in autumn proceeds to flower in 

 spring (KLEBS, 1906, pp. 74, 113), although it does not contain one-hundredth 

 part of the organic nutriment that the autumn beet that has been kept warm 

 during the winter shows in spring ; yet the latter does not flower. Thus, the most 

 important factor is the concentration of the organic nutrients, as also theirrelation 

 to the inorganic. This high concentration, however, must arise from the fact 

 that dissimilation is far exceeded by assimilation. The attainment of such 

 a high concentration may be combined under certain conditions with long- 

 continued vegetative growth, as in Agave or trees. Once attained, however, we 

 observe flowering taking place universally even on slips taken from such a plant. 

 KLEBS quotes certain apposite and interesting observations of SACHS (1892). 



365, 11. 1-5, for Such facts . . . taken from it. read KLEBS himself has (1905) 

 obtained similar results with Sempervivum. 



In this relation we must point out that SACHS interpreted his observations 

 in quite a different way, viz. by his hypothesis of specific organ -forming sub- 

 stances. According to him flowering resulted not from the effect of a certain 

 quantity or concentration of ordinary nutrients on the growing point, but from 

 the presence of materials of a certain quality. Wherever these were present 

 the formation of flowers took place. 



11. 13-16, for The conditions ... of flowers, readWiNKLER's experiments 

 just cited argue not only against SACHS'S but also against KLEBS'S view, in oppo- 

 sition to which many other arguments may be advanced ; we will limit ourselves 

 to the following remarks. When we inquire how, essentially, this alteration 

 in the relationship of assimilation and dissimilation which leads to flower forma- 

 tion arises, we must admit that we have in many cases no answer available. 

 Most instructive is the increase in respiration over the normal in beetroots or 

 rosettes of Digitalis, kept warm through the winter. One might be doubtful, 

 even in the case of the favourable effect of light on flowering, whether an exces- 

 sive concentration of assimilata really takes place ; at all events, the concen- 

 tration would not occur if active vegetative growth used up these materials. 

 One would naturally think of the absence of ash materials which might lead to 

 diminished use of the assimilata in growth. But we cannot co-ordinate this, 

 in itself, very hypothetical explanation with the fact that many flowering 

 plants form both flowering short shoots and vegetative long shoots. If one 

 bud has a sufficient supply of salts to enable it to grow vigorously, how does it 

 come about that another has not ? If the concentration of the assimilata in a 

 bud becomes so great that it forms flowers, how does a dilution arise in the buds 



JOST H 



