384 COOK 



instead of flowers is frequent among the saxifrages and other 

 Arctic plants, though many similar instances are known in natives 

 of temperate and tropical regions. 



Wheat and barley, and to a less degree several other domes- 

 ticated plants, have been unconsciously selected towards autog- 

 amy in a similar manner, by being cultivated far to the north 

 of their original habitats. In unfavorable seasons only the 

 autogamously fertilized seeds would ripen. The wild relatives 

 of all these plants, so far as known, have facilities for cross- 

 fertilization. 



That autogamy and other forms of restricted descent conduce 

 to the breaking up of species into small subspecific groups, is well 

 shown among the cereals. The rye plant has retained and even 

 accentuated its provisions for cross-fertilization, and has kept 

 its position as a relatively normal coherent species, instead of 

 falling apart into distinct varieties. Cross-fertilization has also 

 been fully maintained in the corn plant, but here the large size 

 of the seeds and their compact grouping on the ears greatly facili- 

 tate selection, and have favored the establishment of many local 

 varieties. 



RELATION OF LINIC TO CLONIC PROPAGATION. 



The fact that reproductive fertility deteriorates more rapidly 

 than vegetative vigor, when organisms are placed under condi- 

 tions of restricted descent, is to be correlated with another phe- 

 nomenon, discovered by Darwin, that autogamous fertilization 

 is sometimes superior to more miscellaneous methods of narrow 

 inbreeding. This fact has been generally accepted to mean 

 that autogamy and heterogamy are both normal evolutionary 

 conditions. In the kinetic interpretation it does not appear 

 that autogamy is a truly normal and progressive state. The 

 superiority of strict autogamy over more miscellaneous inbreed- 

 ing appears explainable by analogy with parthenogenesis and 

 vegetative propagation. All three processes can be viewed as 

 methods of postponing deterioration from restricted descent, by 

 omitting the nuclear readjustments which are required in normal 

 sexual reproduction. When diversity of descent is no longer 

 sufficient for normal readjustments, degeneration begins, in the 

 form of mutative variations. These usually fall below the 



