May 4, 1906.] 



SCIENCE. 



685 



iimnediately germane to the subject under 

 discussion, and they can be more fully 

 described. But before proceeding to a 

 discussion of them, the factors that lead 

 to the phenomena of ever-sporting should 

 be analyzed. According to de Vries, 



The wide range of variability of ever-sporting 

 varieties is due to the presence of two antagonistic 

 characters which can not be evolved at the same 

 time and in the same organ, because they exclude 

 one another. Whenever one is active, the other 

 must be latent. But latency is not absolute in- 

 activity and may often only operate to encumber 

 the evolution of the antagonistic character, and to 

 produce large numbers of lesser grades. 



On a subsequent page, he says of the 

 characters : 



They might be termed alternating, if it were 

 only understood that the alternation may be com- 

 plete or incomplete in all degrees. Complete 

 alternation would result in the extremes, the in- 

 complete condition in the intermediate states. 

 In some eases, as with the stocks, the first pre- 

 vails, while in other cases, as with the poppies, 

 the very extremes are only rarely met with. 



De Vries says: 



Taking such an alternation as a real character 

 of the ever-sporting varieties, a wide range of 

 analogous cases is at once revealed among the 

 normal qualities of wild plants. Alternation is 

 here almost universal. It is the capacity of 

 young organs to develop in two divergent direc- 

 tions. 



These phenomena are illustrated by 

 numerous illustrations drawn from those 

 presented by wild plants. The water- 

 persicaria, Polygonum amphibium, is the 

 one first cited. This plant occurs in two 

 forms, one aquatic and the other terres- 

 trial. The aquatic plants, known as var. 

 nutans, "have floating or submerged stems 

 with oblong or elliptical leaves, which are 

 glabrous and have long petioles. The ter- 

 restrial plants (known as var. terrestre or 

 terrestris) are erect, nearly simple, more 

 or less hispid throughout, with lanceolate 

 leaves and short petioles, often nearly ses- 

 sile." These "two varieties may often be 



seen to sport into one another. They are 

 only branches of the same stem grown 

 under different conditions." 



Numerous other instances of double 

 adaptation are given. Those taken from 

 alpine plants transferred to the lowland 

 are in some respects the most interesting 

 for our discussion. De Vries says : " It is 

 simply impossible to decide concerning the 

 real relations between the alpine and low- 

 land types without experiments." Some 

 experiments are given by which the factor 

 determining the change in character was 

 discovered. 



In concluding his remarks on these phe- 

 nomena, the statement is made : 



Useful dimorphism or double adaptation, is a 

 substitution of characters quite analogous to the 

 useless dimorphism of cultivated ever-sporting 

 varieties and the stray occurrences of hereditary 

 monstrosities. The same laws and conditions pre- 

 vail in both cases. 



Interjected into this chapter is a consid- 

 eration of the 'Theory of Direct Causa- 

 tion,' first advanced by Lamarck, subse- 

 quently advocated by Nageli, von Wett- 

 stein, Strasburger and other German bot- 

 anists, also by Hyatt, Cope and others in 

 this country. The instances of double 

 adaptation, of course, do not support this 

 theory. De Vries gives an account of some 

 plants that grow in the Desert of Kaits, 

 Ceylon. These plants, although they have 

 apparently grown in the desert for many 

 centuries, have not become of the desert 

 type, still possessing a thin epidermis and 

 exposed stomata; and were shown by Hol- 

 termann to lose the only desert character 

 that they had, their dwarf stature, when 

 grown on ordinary garden soil. These 

 plants disprove the Nagelian contentions: 

 (1) That extreme conditions change or- 

 ganisms in a desirable direction; (2) that 

 the only change induced by the dry soil, 

 decreased stature, was not hereditary. 



V. Mutations.— Under this heading are 



