SCIENCE 



[N.S. Vol. XXXI. No. 806 



spread at all becomes more energetic 

 through the constant mixing of blood of 

 the advancing population. All these ideas 

 are interesting, but difficult, if not impos- 

 sible of experimental proof. The last sug- 

 gestion receives some support from the fact 

 that many weeds and other organisms 

 "peter" out after they have ceased to 

 spread. The recent examples of the Rus- 

 sian thistle and the prickly lettuce are 

 familiar cases. Such phenomena may be 

 due wholly or in part to increase in enemies 

 —but in many eases like the two cited 

 there is no iota of positive evidence. I 

 think we ought to give such phenomena 

 more consideration, as they reveal traits 

 in plants that transcend all of our 

 stereotyped and inadequate theories. The 

 old gardener often treats his plants as if 

 he regarded them as sentient beings. Per- 

 haps we err in considering them too much 

 as machines. 



I have touched thus much on the botany 

 of our cultivated plants and their origin 

 and behavior under domestication because 

 I believe that there lies here a great field 

 for botanical and agricultural advance- 

 ment. It matters not what we call this 

 phase of botany— its successful prosecution 

 ■demands both broad and intensive botan- 

 ical training. It requires at least a good 

 knowledge of systematic botany, of plant 

 physiology and of the theories and prin- 

 ciples of plant breeding and plant evolu- 

 tion. One must at least know aU the bot- 

 any possible of the plants he is immediately 

 concerned in breeding, lest he be lured into 

 needless error. Among his many experi- 

 ments, Mr. Oliver has made some very in- 

 teresting hybrids of Poa arachnifera, the 

 Texas bluegrass and Kentucky bluegrass, 

 a circumboreal plant. His culture soil was 

 presumably sterilized, yet mixed with his 

 hybrids were plants of Canada bluegrass, 

 Poa compressa. One enthusiastic Men- 



delist was jubilant over the supposed dis- 

 covery of the origin of this grass and at 

 once proposed an additional series of ex- 

 periments. Now Poa compressa is a Euro- 

 pean species— and the securing it by cross- 

 ing a Texas species with common bluegrass 

 •was certainly a startling phenomenon. For- 

 tunately or perhaps unfortunately, some of 

 the other supposed hybrids in the lot 

 turned out to be other grasses, including 

 timothy and sweet vernal grass, so that the 

 source of the error was evident. It points, 

 however, clearly to the necessity of the 

 scientific breeder knowing the systematic 

 botany at least of the group he is working 

 with. 



I well recall that when I first began to 

 study plants I promptly found about a 

 dozen species of red clover— at least they 

 were different from each other. It took a 

 long time to teach me that in plants there 

 were differences and differences, some of 

 which should be taken seriously and others 

 ignored. In general, I was taught that any 

 differences that existed in closely related 

 cultivated plants were to be ignored, but 

 in wild plants they would usually have to 

 be considered. It is really very fortunate 

 for the cultivated plants that systematic 

 botanists have not taken their differences 

 seriously, otherwise we would have chaos 

 indeed. It is unfortunate that the con- 

 servatism which most systematic botanists 

 exhibit toward cultivated plants should 

 not be exhibited as well toward wild plants. 

 If more attention had been given to the 

 cultivated plants, think what a vast host of 

 reputed wild species would have escaped 

 the pangs of christening. There used to 

 be hope that after a while all the species 

 would be described- so that systematic 

 botanists could devote themselves to deeper 

 studies. But alas, it seems only necessary 

 to make finer distinctions to reveal a won- 

 drous display of so-called species where 



