444 KINSHIP AND ADAPTATION 



It has been thought l)y man}' naturahsts that the differ- 

 ences among plants and animals may best be accounted for 

 as peculiarities which have arisen in individual acquire- 

 ments, these having become hereditary and thus characteris- 

 tic after many generations of similar response to a similar 

 enviromnent. Suppose, by way of example, that some of 

 the seedlings from primitive marsh-marigolds grew in a 

 rather dry locality and were more or less shaded by over- 

 growth. They might be expected to respond to the lessened 

 light by elongation of the internodes and leaf-stalks, while a 



Fig. 302. — Pigmy Buttercup (Rnnu?iculus pygmwus, Crowfoot Family, 

 RanunculacecE) . Plant. Flower. Fruit. (Britton and Brown.) — 

 Perennial (?) herb 5-12 cm. tall; flowers yellow; fruit dry. Native 

 home; northern America and Eurasia. 



finger-like lobing of the blades through increased growth along 

 the ribs and scant growth of the pulp between the stem 

 would be fortunate as enabling the leaves to catch more of 

 what little light there was. But the less favorable conditions 

 for food-making would render it impossible for them to form 

 and feed as many seeds as the marsh plants had done; hence 

 some of the later-formed ovules would be more or less starved. 

 From the good seeds formed by these pioneer plants and 

 scattered in the vicinity, a second generation would arise, 

 the individuals of which would respond similarly to the same 

 trj'ing conditions. Innumerable generations might follow, 



