CONDITIONS OF GAMETE FORMATION 371 



by altering the rate of metabolism, or in some other way, and so 

 lead to vegetative or other forms of agamic reproduction. 



From this point of view, the absence or rare occurrence of 

 gametic reproduction in various plants, either in nature or under 

 cultivation, is not in any sense the factor which determines increased 

 agamic reproduction, but the agamic reproduction prevents the 

 organism from attaining the physiological condition in which 

 gametic reproduction occurs. Teleological interpretation of such 

 cases is entirely unnecessary and beside the point. Whether one 

 form of reproduction or another occurs depends upon the physi- 

 ological condition of the individual. In the physiologically 

 young, immature individual, whether it be a unicellular plant, a 

 single plant axis, or a whole multiaxial plant, reproduction, when it 

 occurs, is agamic, while the formation of gametes occurs in the older, 

 mature individual. 



This conclusion may seem at first glance to conflict seriously with 

 certain other observational and experimental data concerning the 

 occurrence and experimental production of flowers. Flowers appear 

 frequently, either as an anomaly in nature or under experimental 

 conditions, on plants which, as regards length of time from the seed, 

 as well as size and morphological condition, are in an early stage 

 of development and young. The experimental investigations of 

 Vochting, Klebs, and others have demonstrated that the occurrence 

 of flowering may be controlled within wide limits by means of 

 various external conditions. 1 



Vochting's experiments on Mimulus tilingii show very clearly 

 the significance of light for flowering. In a certain low illumination 

 in which vegetative growth is possible the inflorescence begins to 

 develop, but the preformed flower buds cease their development at 



1 The following references will serve as a guide to the literature of the subject. 

 Mobius ('97) presents and describes numerous facts, largely observational rather 

 than experimental, bearing upon the problem. Diels ('06) has brought together many 

 cases of premature flowering or "nanism," both from his own observations and from 

 the literature. The experimental investigations of Vochting ('93), Klebs ('03, '04, 

 '06), and others demonstrate that the occurrence of flowering may be controlled within 

 wide limits by means of external factors. Jost ('08, pp. 439-46) gives a good general 

 survey of the subject. Additional references are Benecke, '06; Dbposcheg-Uhlar, '12; 

 A. Fischer, '05; Goebel, '08, pp. 6, 10, 117, 190; Loew, '05. These papers contain 

 further references. 



