SPECIES AND VARIETIES : THEIR ORIGIN BY MUTATION 167 



Similarly with regard to Rubrtxerfis, — Stem more slender ; bracts 

 narrower (spikes and flowers same as of CE. Lam.) ; veins red (but not 

 absolutely lacking in CE. Lam.) ; leaves narrower ; stem and leaves very 

 brittle, due to turgidity and a weak development of bast, &c. 



Now, I do not think that any florist, much less a systematic botanist, 

 would regard these characters as more exceptional than may be found 

 in many a "form" of cultivated plants, such as occurs in the Cabbage 

 tribe, root-crops, in Darwin's " Hero " among Ipomoeas, of which he says, 

 " The self-fertilised children of ' Hero ' certainly inherit the powers of 

 growth of their parents," &c* A similar permanency existed in his 

 white Mimulus. 



De Yries observes that it is often difficult to decide whether a given 

 form belongs to one or another of these groups (p. 564). So here, gigas 

 has reduced internodes, ovary and number of seeds: such "losses" 

 ought to make it a " variety ' ' ; while the more numerous leaves and 

 larger corollas and larger seeds may be regarded as " gains," which entitle 

 it to be an " elementary species." 



But now there is a very suspicious fact about nearly all his forms, 

 which betrays itself in his descriptions. Thus, of rubrhiervis, oblong a, and 

 nana, they are all characterised by a " brittleness " ; albida, by chlorosis 

 and by being a "very weak species." Oblonga is, as an annual, "very 

 slender and weak " ; and if oblonga be a biennial, it is "a low plant with 

 a limp stem. This and its branches have bent tips, and both are very 

 brittle." 



It is impossible not to see that all these feeble productions are 

 suffering from some sort of degeneracy or other, probably arising from 

 a too moist and too richly manured soil. 



De Vries does not tell us how his borders were prepared ; but it is to 

 be gathered from the following paragraph, which shows how various 

 individual differences arise from minute differences in the soil. 



Speaking of the external causes of the individual differences among 

 seedlings, he says (p. 720): "Moisture and manure differ on different 

 portions of the same bed in a way unavoidable even by the most careful 

 preparation. Some seeds germinate on moist and rich spots, while their 

 neighbours are impeded by local dryness or by distance from manure. 

 Some come to light on a sunny day and increase their first leaves rapidly, 

 while the following day the weather may be unfavourable and greatly 

 retard growth. The individual differences seem to be due, at least in 

 a very great measure, to such apparent trifles." 



The" immediate cause, then, of these characters seems to be excessive 

 moisture and over-nourishment, tending to make the tissues too succulent 

 and consequently brittle, as well as to intensify the production of foliage 

 in gigas ; and, on the other hand, to reduce the number of seeds and size 

 of the fruit. 



Unless I misunderstand him, De Vries does not always seem to be 

 quite consistent. He lays great stress on " constancy," and observes that 

 Wittrock describes several local types (of pansies) which proved to be 

 constant in his pedigree cultures. Some of them produced other forms 

 (pp. 42, 43). Therefore they were not altogether constant. Similarly, 

 * Cross and Self Fertilisation, p. 48. 



