ANOTHER MODE OF SPECIES FORMING 265 



The fact that crossing was only the first step and that selection 

 from the numerous variations secured in the second and a few succeed- 

 ing generations was the real work of new plant creation had never 

 teen appreciated; and to-day its significance is not fully understood 

 either by breeders or even by many scientific investigators along these 

 very lines. Old tailings are constantly being worked over at great ex- 

 pense of time and with small profit, while the mother lode is repudiated 

 and neglected. 



Plant breeding to be successful must be conducted like architecture. 

 Definite plans must be carefully laid for the proposed creation; suit- 

 able materials" selected with judgment, and these must be securely 

 placed in their proper order and position. ISTo occupation requires more 

 accuracy, foresight and skill than does scientific plant or animal 

 breeding. 



As before noted, the first generation after a cross has been made 

 is usually a more or less complete blend of all the characteristics of 

 both parents; not only the visible characters, but an infinite number of 

 invisible ones are inherent and will shape the future character and 

 destiny of the descendants, often producing otherwise unaccountable 

 so-called mutations, saltations or sports, the selection and perpetuation 

 of which give to new plant creations their unique forms and often 

 priceless values, like the Burbank potato produced thirty-six years ago 

 and which is now grown on this western coast almost to the exclusion 

 of all others (fourteen millions of bushels per annum, besides the vast 

 amount grown in the eastern United States and other countries), or 

 the Bartlett pear, Baldwin apple and navel oranges, all of which are 

 variations selected by some keen observer. Millions of others are 

 forever buried in oblivion for the lack of such an observer. 



But in this paper I wish to call attention to a not unusual result of 

 crossing quite distinct wild species which deserves the most careful 

 analysis, as it seems to promise a new text for scientific investigation, 

 especially on biometric lines. The subject was most forcibly brought 

 to my attention twenty years ago by the singular behavior of the 

 second-generation seedlings of raspberry-blackberry hybrids. By cross- 

 ing the Siberian raspberry (Rubus cratwgifolius) with our native 

 trailing blackberry {Rubus vitifolius), a thoroughly fixed new species 

 was summarily produced. The seedlings of this composite Rubus 

 (named Primus), though a most perfect blend of both parents but re- 

 sembling neither, never reverted either way; all the seedlings coming 

 much more exactly like the new type than do the seedlings of any 

 ordinary wild rubus. Many thousand plants have been raised genera- 

 tion after generation, all repeating themselves after the new and 

 unique type. No botanist on earth could do otherwise than classify 

 it if found wild as a valid new species, which it truly is, though so 

 summarily produced by crossing. 



