200 DYNAMICS OF LIVING MATTER 



If the tip of the stem alone is put into the dark, while the leaves are 

 exposed to the light, the tip forms blossoms. Therefore Sachs con- 

 cluded that in the light the leaves form substances which are of specific 

 importance for the formation of flowers. He found in support of this 

 view that bulbs of tulips, hyacinths, iris, and crocus, if they are caused 

 to grow in the dark during the spring, produce normal blossoms. In 

 these plants the material and the specific substances necessary for the 

 formation of their flowers were stored up during the preceding year. 

 Sachs generalized this conclusion : Not the quantity of material alone 

 but also the quality is decisive for the formation of organs. There 

 are as many specific substances in a plant as there are different organs. 

 It is obvious that this idea is in full harmony with the experiments of 

 Mendel and De Vries on heredity, inasmuch as this theory ultimately 

 forces us to assume specific substances as the determinants for the 

 hereditary qualities. 



To make Sachs's hypothesis as clear as possible, we will quote the 

 following passage: "We may imagine the process (of organization) 

 as being in a way comparable to the successive processes in a chemical 

 factory, where from the original raw material chemical compounds of 

 the greatest variety are formed in succession until the final product 

 is obtained chemically pure, possibly in an extremely small quantity. 

 Although our analyses seem to indicate apparently always the same 

 protoplasm, starch, sugar, fat, we must realize that these substances 

 may themselves differ,* or that traces of other substances may force 

 them to solidify in different organic forms. To give one example, 

 it seems that the formation of flowers and seeds depends upon a 

 storing up of phosphates in these organs, that the plant cannot form 

 flowers and seeds until there is a comparative excess of phosphates com- 

 pared with the other ashes in the saps. . . . An excess of phosphates 

 may force a beet to produce flowers in the first instead of the second 

 year." Sachs applied the same idea to the problem of regeneration. 

 If we cut a piece from the branch of a willow tree, it will under the 

 proper conditions, form roots near the basal and shoots near the apical 

 end. Sachs raises the question as to how it happens that the cutting 

 off of a piece causes the formation of organs in places where it would 

 never occur without this operation or other disturbing conditions. The 

 question is answered by Sachs in harmony with his above-mentioned 

 hypothesis. Duhamel had assumed the existence of two currents of 

 sap in the plant, one ascending, the other descending ; the latter carry- 

 ing root-forming, the former stem-forming, material. Sachs imagines 

 that "as long as a green plant with an upright stem is nourished and 



* E.g. Stereoisomeres. 



