APPLICATIONS OF RESULTS OF RESEARCHES. 



369 



of the hybrids studied in this research in respect to its 

 macroscopic and microscopic characters, has been found 

 to so differ from its parents that were it not known to 

 be a hybrid there would be ample justification to regard 

 it as a species (see Ipomoea, Part II). It is well known 

 to the botanist that many of the hybrids included among 

 the hundreds referred to by Foeke are so individualized 

 as to warrant their assignment as species or subspecies. 

 Finally, it seems from the present state of our knowl- 

 edge that the difficulty of hybridization, the tendency 

 to infertility of the offspring, the tendency to the develop- 

 ment of characters in the hybrid in excess of parental ex- 

 tremes, and the tendency to develop new characters in the 

 hybrid, bear usually an inverse relationship to the near- 

 ness of the parents, while the tendency to intermediate- 

 ness bears usually a direct relationslup. Owing, how- 

 ever, to the extreme plasticity of protoplasm the most 

 variable results in hybridization are to be expected, as 

 is indicated by the results of the studies of the starches, 

 as presented particularly in Table H, Parts 1 to 26, and 

 summaries. 



The study of the genesis of species is without doubt 

 a study of the evolution of chemical compounds, and 

 essentially of interactions, rearrangements, and com- 

 binations of stereochemic systems and their compon- 

 ents. In the origin of species by hybridization there is, 

 according to the conception stated in the penultimate 

 section, a union of two stereoisomeric systems of vary- 

 ing plasticities, female and male, in each of which there 



are assumed to be potentially every or practically every 

 character and character-phase of the parent. More- 

 over, this variability of plasticity applies not only to the 

 system, as a whole, but also to each of the integral stereo- 

 chemic units. Having extremely complex, plastic, in- 

 teracting systems, and applying thereto a fundamental 

 knowledge of physical chemistry, especially of organic 

 colloids, as is indicated, it seems that there should be 

 no more difficulty than in the reactions of organic sub- 

 stances generally in reaching satisfactory theoretic un- 

 derstandings of the diverse developmental changes that 

 occur in the hybrid — that is, why some characters are 

 like those of one or the other parent or both parents, or 

 developed beyond parental extremes, or new characters 

 appear; or why one parent may be of equal or greater 

 potency in influencing the development of the characters 

 of the hybrid ; or why species of remote genera can not 

 be crossed, or, on the other hand, why varieties of the 

 same species may readily be crossed; or why characters 

 that may have existed in ancestral generations, but which 

 are not apparent in the parents, may appear in the off- 

 spring; or why there may or may not be Mendelian 

 inheritance; or why mutations can be induced arti- 

 ficially by the injection of certain substances into the 

 ovaries, etc., etc. Unfortunately this subject is so vast 

 that a detailed consideration of such points would take us 

 far beyond the possible limits of space of this report, and 

 therefore, as previously stated, nothing more can be 

 offered at present than mere suggestions. 



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