XIV FUNDAMENTAL TROBLEIMS 431 



hy}30gynous poppies, pinks, and St. John's "worts have abund- 

 ance of seed and rather scanty foliage ; while the epigynous 

 dogwoods and honeysuckles have few seeds and abundant 

 foliage. If, instead of the number of the seeds, Ave take the 

 size of the fruit as an indication of reproductive energy, we find 

 this at a maximum in the gourd family, yet their rapid and 

 luxuriant growth shoAvs no diminution of vegetative power. 

 So that the statement that plant modifications proceed " along 

 an absolute groove of progi-essive change " is contradicted by 

 innumerable facts indicating advance and regression, improve- 

 ment or degradation, according as the ever-changing en\aron- 

 ment renders one form more advantageous than the other. 

 As one instance I may mention the Anonacese or custard-apple 

 tribe, Avhich are certainly an advance from the Ranunculacese ; 

 yet in the genus Polyalthea the fruit consists of a number of 

 separate carpels, each borne on a long stalk, as if revei'ting to 

 the primitive stalked carpellary leaves. 



On the Origin of Spines. 



But perhaps the most extraordinary application of the 

 theory is that Avhich considers spines to be an indication of the 

 " ebbing vitality of a species," and Avhich excludes " mammalian 

 selection altogether." If this were true, spines should occur 

 mainly in feeble, rare, and dying-out species, instead of which 

 Ave have the haAvthorn, one of our most vigorous shrubs or trees, 

 Avith abundant Adtality and an extensiA^e range OA^er the whole 

 Palsearctic region, shoAA'ing that it is really a dominant species. 

 In North America the numerous thorny species of Crataegus 

 are equally vigorous, as are the false acacia (Robinia) and 

 the honey-locust (Grleditschia). Neither have the numerous 

 species of very spiny Acacias been noticed to be rarer or less 

 A^gorous than the unarmed kinds. 



On the other point — that spines are not due to mammalian 

 selection — Ave are able to adduce what must be considered direct 

 and conclusive evidence. For if spines, admittedly produced by 

 aborted branches, petioles, or peduncles, are due solely or mainly 

 to diminished vegetativeness or ebbing vitality, they ought to 

 occur in all countries alike, or at all events in all Avhose similar 

 conditions tend to check vegetation ; AA'hereas, if they are, 

 solely or mainly, developed as a protection against the attacks 



