December, 1910.] 



539 



Miscellaneous. 



ling. Aaronsohn has recently dis- 

 covered in the mountains of Palestine 

 what are probably the wild originals of 

 wheat, of barley and of rye. As this 

 country was long ago well explored 

 botanically, the question at once arises, 

 why were not these plants found? 

 Aaronsohn offers a humorously simple 

 explanation, namely, that no botanist 

 ever collects a cultivated plane and no 

 agronomist ever looks afc a wild one. 

 Perhaps a similar explanation may ac- 

 count for our ignorance of corn and 

 other American natives in the wild 

 state. A particular interest in kuowing 

 the wild form of such plants is to be 

 able to measure the progress that has 

 been made by cultivation. Another is 

 to determine how quickly it may be 

 possible to breed up to the approximate 

 standard of the long cultivated strains. 

 There is a general belief that great 

 improvements can be made in the early 

 processes of breeding for improvement, 

 but these rapidly and progressively 

 become less and less with each step in 

 advance. This is perhaps true as it is a 

 general law of nature. Yet the improve- 

 ment made in some supposed cases is 

 vastly greater than could possibly have 

 been anticipated. Thus the gap from 

 Johnson grass to its supposed deriva- 

 tions, such as Kafir, Jerusalem corn, 

 milo, Sumac sorghum and a host of 

 other varieties is so great as to stagger 

 one's belief. Yet the botanical evidence 

 is good enough to warrant critical ex- 

 'perimental investigations. 



How much further wheat, corn and 

 other long-cultivated plants may still be. 

 improved cannot be foretold, because 

 we are too ignorant of the potentialities 

 which have brought them to their pre- 

 sent development. In any attempt that 

 may be made to redevelop the culti- 

 vated forms from the wild forms, two 

 things will have to be considered— first, 

 that various forms of the wild plant may 

 and probably do exist in different 

 regions ; and second, that even beginning 

 with the same wild form its descendants 

 in different regions will probably vary 

 in different directions. Only on one 

 or both of these hypotheses can we 

 explain the fact that with anciently 

 cultivated plants each region has its own 

 peculiar varieties and types. The pro- 

 blem of the origin of the more marked 

 varieties of the plants cultivated in and 

 since historic times becomes an exceed- 

 ingly complex one, probably capable of 

 being duplicated only in small part. We 

 must not underestimate the ability of 

 even very low races of agricultural 

 people to improve their cultivated plants. 

 Certainly the Indians developed corn to 



a very high degree and had some pretty 

 clear ideas regarding its culture. For 

 example, the Virginia Indians made it 

 a point to plant in each hill seed from 

 several different ears. 



It seems to me that we often err on 

 the side of making phenomena appear 

 more simple than they really are. Plants 

 are vastly more complex organisms than 

 our formulated ideas recognise. Many 

 of their phenomena completely baffle us. 

 For example, I might mention what has 

 been called aggressiveness in a plant — 

 namely, its ability not only to occupy 

 and maintain the soil, but to spread and 

 crowd out other plants. This is parti- 

 cularly evident in plants introduced 

 from one country to another. Thus 

 nearly all of our weeds are of old world 

 origin. The same is true of our per- 

 manent meadow and pasture plants, 

 where ability to occupy and hold the 

 ground against weeds is essential. In 

 this respect our American grasses and 

 clovers utterly fail before the foreign 

 immigrants. Some other striking in- 

 stances of the great aggressiveness of an 

 immigrant may be cited. The introduced 

 English violet is said to be the worst 

 of weeds in Mauritius ; American cacti 

 are becoming a pest in South Africa; 

 the marvellous vigour and spread of the 

 American water weed Elodea under 

 European conditions is well-kuown. 

 Several explanations of these and similar 

 phenomena have been advanced. The 

 commonest one is that the plant is in- 

 troduced but its fungus and insect 

 enemies are not. Therefore the plant is 

 released from all handicaps as it were and 

 can exercise to the utmost its inherent 

 energy. A second and related explan- 

 ation is that every plant becomes held 

 within limits by the competition of 

 other plants in its native land, and very 

 often in the new environment the native 

 plants do not have an equal restraining 

 influence — because they have had to 

 contend with a different set of competi- 

 tors. A third idea is that any organism 

 with the ability to spread at all becomes 

 more energetic through constant mixing 

 of blood of the advancing population. 

 All these ideas are interesting, but 

 difficult, if not impossible of experi- 

 mental proof. The last suggestion re- 

 ceives some support from the fact that 

 mauy weeds and other organisms 

 "peter" out after they have ceased to 

 spread. The recent example of the 

 Russian thistle and the prickly lettuce 

 are familiar cases- Such phenomena 

 may be due wholly or in part to increase 

 in enemies— but in many cases like the 

 two cited there is no iota of positive 

 evidence. I think we ought to give such, 



