MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 85 



A condition similar to the above has been found in Crataegus by Sargent 

 & Peck, who say (1906) : 



The peculiar tendency of Crataegus to flock together is strikingly illustrated in our terri- 

 tory. It is rare to find any large area occupied by a single species. Where many thorn 

 trees and bushes grow together there are usually many species. A remarkable example of 

 this kind is found in a narrow strip of pasture land bordering the Erie Canal near Menands. 

 Here 10 species are growing in an area of about i acre. The closest condensation of num- 

 erous species that I have seen anywhere is near Albia, where 9 of our native species are 

 growing in a kind of irregular row along the west bank of the Wyantskill Creek. The 

 length of the row is about 100 feet. It is worthy of remark that 3 of these species, Cratae- 

 gus ferentaria, C. rhombi folia, and C. succulenta, belong to the group Tomentosae. Such 

 close associations of members of a single group as this one at Lansingburg are very signif- 

 icant and when more fully understood may possibly throw some light on the interesting 

 problem of the development of species. 



Other students of the thorns have found similar conditions with strains 

 which were found to be distinct and hereditary in pedigreed cultures. Here, 

 again, if a conservative view is upheld and specific rank is not accorded these 

 clearly separable elementary species, a similar association of the closely 

 related group species may be found. A similar condition among the opuntias 

 has been noted by the author. These facts make it conclusive that the 

 assumption that the nearly related or most nearly related species of a group 

 do not occupy the same habitat is untenable. 



Two bud-sports of different types as to origin were found during the 

 summer of 1905 and tested as to their hereditary qualities. 



The vegetative mutant branch of ammo phi! a was seen to give rise to a 

 progeny which came true to the characters of the branch producing the seeds 

 from which they were grown, and the reversion, if it is such, may be consid- 

 ered complete. If, as suggested, ammophila is a hybrid and the sport is a rever- 

 sion to one of the parents, then this case may be taken to agree with that noted 

 by De Vries (1900, p. 86), in which a hybrid of two forms of Veronica gave off 

 bud-sports, which in purely fertilized seeds came wholly true to one of the 

 parental types. In this case the sport was a reversion to the ancestral qualities 

 which had become latent when the hybridization was effected. 



The second bud-sport was one in which the recessive characters appeared on 

 a branch in the first generation of a cross, and when this was purely fertilized 

 showed only a strict inheritance of the recessive characters. 



The facts offered by bud-sports have much significance as to the localization 

 of mutations, and as to the nature of the stimuli which set the mutatory pro- 

 cesses in action. Primary buds usually arise laterally from the tip of the 

 growing point and within a millimeter or two from its apex. The saltation, 

 of whatever character it may be, occurred in a cell or cells in the embryonic 

 tissue while the growing tip was moving upward a distance of a millimeter or 

 more. Much depends upon the place where this occurs. If it is possible for a 



