HORTICULTURAL SOCIETY OF NEW YORK. 



of natural selection was too slow to account for the development of new species. 

 His first step was to take loo plants, native and cultivated, and watch to see 

 what happened. Out of these it was observed that Oenothera Lamarckiana did 

 not come true from seed. In 1887 he saw some plants of this in a potato field — 

 thousands of them — some of which were unlike their parents. He gathered 

 seed and sowed it so the next year he had 50,000 seedlings, out of which 334 did 

 not agree with the parents and even differed among themselves. They belonged 

 to ten or twelve types, however, and continuing the work he had some sixteen 

 types after three or four years. By a reference to the plants which Dr. Mac- 

 dougal had brought with him he illustrated the appearance of 14 distinct types 

 in his own seedlings raised at the New York Botanical Garden. These were 

 very distinct and varied in form of leaf, in size, and otherwise. Some of these 

 had been indentified as species. 



There vv^ere no gradations among them. They did not show connecting 

 links. Out of 100 seedlings, three to five were mutants. The essential points of 

 mutation were these ; That they come off without any connecting 

 types ; that they are, so to speak, side steps, and not progressive 

 developments from the parent. The third point — and it was a puzzle to the 

 botanists — were the mutants going to exterminate the parent? It was hardly 

 likely, if we considered the small proportation of new forms. Ninety-five per 

 cent, came true. Figure that the species goes on year by year. O. Lamarckiana 

 would yield, say 200,000 seeds. Only 5 per cent, are of new forms, and they 

 may not be adapted to the conditions. So it must take the new plant a very 

 long time to get ahead. That species were developed by this sudden method 

 was pretty clear if we thought of the age of the earth. It is not old enough 

 to have allowed the development of all the species now found upon it by the slow 

 method of natural selection. But natural selection accompanied the saltatory 

 origin of species. New forms were developed, but only such as best fitted the 

 situations survived. The others die off. 



One must not think that Oenothera is the only plant showing mutations. 

 Discontinuous variation appeared elsewhere as in monstrous flowers, also the 

 doubling of florists' flowers and the singling of those that were double offered 

 evidence of discontinuous variation. If it were wanted to see if a plant were 

 mutating, get a pure species, get pure soil — he used steam sterilized soil — 

 and grow the seedlings where they can remain undisturbed. Look carefully 

 at the young plants and preserve every "unlike" form; weed out duplicates 

 only, to avoid the charge of destroying the connecting links. This is, of course, 

 the exact reverse of garden culture practices. 



Dr. Macdougal exhibited also a mutant form of the native evening primrose 

 (O. biennis) ; he had recognized one out of several thousand seedlings saved 

 from the wild plants in the garden — but then, oerhaps, he was not keen enough 

 to recognize all the variations. The mutants vary in succeeding generations, 

 but do not vary toward the parent, and the variation is greater in them than 

 in the old species. 



In reply to a question the lecturer stated most positively that no per- 

 manent alteration in a plant had ever been brought about by conditions of 

 cultivation ; that new developments under cultivation v/ere mutant forms and 

 must be so accorded. 



14 



