THE AMERICAN NATURALIST [Vol. XLIII 



Evidence against the reality of adaptation in a sub- 

 jective sense has been accumulating. At first sight the 

 increase of cutin in plants exposed to increasingly xero- 

 phytic conditions, or the increased development of air 

 chambers in plants exposed to increasingly hydrophytic 

 conditions look like adaptations, and such changes cer- 

 tainly seem advantageous. However, there are facts that 

 point in another direction. There is no more important 

 source of strength in plants than that afforded by bast 

 and similar mechanical tissues. Yet recent experi- 

 menters have failed to get any significant response in 

 the way of great bast development by exposing growing 

 organs to considerable tension. Bast primordia, how- 

 ever, are very plastic and respond readily to changes in 

 moisture. Thus we have in bundles of bast fibers tissues 

 that do not adapt themselves to a demand for tensile 

 strength, although such a response would be highly ad- 

 vantageous ; on the other hand, they respond to increased 

 transpiration, although it has not been claimed that bast 

 fibers are of especial value in checking transpiration. 

 Again, increased conduction, whether due to high tran- 

 spiration or other causes, often results in an increased 

 development of the vascular tract. The advantage of 

 such a modification is at least dubious in xerophytes, but 

 the case is much more striking in such plants as Arte- 

 misia, when parasitized by Orobanche. The Artemisia 

 root is stimulated to excessive development by the attack 

 of the parasite, and examination shows that the vascular 

 tract in particular is greatly increased. If this change 

 in the Artemisia root is an adaptation, it is an adaptation 

 for the Orobanche and not for itself, and what adapta- 

 tionist could expect a plant to be so altruistic as all this? 

 Similar phenomena are seen in fungus and insect galls, 

 and in the cynipid galls in particular, food accumulates 

 in large amount in definite layers around the larval cham- 

 ber. Can the oak be supposed to be so thoughtful for the 

 insect as to provide it food? Or, if one chooses the other 

 horn of the dilemma, can the insect be supposed to have 



