REPRODUCTION 263 



berry, the suckers of lilac and Sequoia,* the stolons, off- 

 sets, runners, etc., of other plants, illustrate this matter. 



In the spore mode of non-sexual reproduction single cells 

 or pairs of cells, each capable of forming a new plant, are cut 

 off by the parent. These reproductive bodies, like the vege- 

 tatively reproductive bodies above mentioned, contain and 

 continue the substance and the condition of the one parent. 

 So soon as they are separated from the parent, they may 

 be so influenced by the factors of their environment as to 

 depart from the character of their parent, to vary. 



The new individuals produced by non-sexual means are 

 usually more numerous than those produced sexually. Non- 

 sexual reproduction is especially the means by which the 

 species is multiplied. Many species, however, have only one 

 means of reproduction, hence the two ends, of maintaining 

 and of multiplying the species, are met by the same means. 

 Many organisms, however, endowed with both means of 

 reproduction, employ one at one time, another at another 

 time. What determines the organism in its behavior? And 

 what are the advantages of each mode? The first ques- 

 tion is answerable at the present time through the already 

 available means of experimenting; the second is not defi- 

 nitely answerable now, though the interpretation of what 

 is observed in nature, and speculation partially supported 

 by experiment, suggest probable answers. From OEdogomum 

 and Coleochivte among the green algfe to the highest of the 

 flowering plants, the phenomenon of alternating generations 

 is one of the most conspicuous in the life of plants. How 

 this has originated and the influences which now control it 

 constitute one of the most intricate problems in morphol- 

 ogy and physiology, the solution of which remains, how- 

 ever, hidden in the future. 



The preceding chapter has shown us that the size, form, 

 color, rate of growth, direction of growth and of move- 

 ment, and many other characters, represent the reaction of 

 the organism to the external influences,- its response to the 

 stimuli, which are collectively termed its environment. We 



* Peirce, G. J. Studies on the coast redwood. Proc. Cal. Acad. Sciences. 

 3d series, Botany, vol. II., 1901. 



