48 Experimental Zoology 



ing, therefore, a high average of carpels), and keep them under 

 favorable conditions, the average of carpels of the race can be 

 temporarily increased. Conversely, if we select the less vig- 

 orous plants, and put them under unfavorable conditions, the 

 accessory carpels can be made to disappear. 



This connection between individual vigor and the forma- 

 tion of carpels is not an absolute one, for there are means by 

 which vigorous plants can be obtained without accessory car- 

 pels. If very young plants are transplanted, and then put under 

 favorable conditions, vigorous plants result without or with few 

 carpels. The interpretation that de Vries gives of this result 

 is that the flower buds were not laid down at the time of trans- 

 planting, but develop soon afterward, when the conditions are 

 temporarily unfavorable. Later, when the favorable conditions 

 begin to act, the rest of the plant responds, but it is too late to 

 affect the carpel formation. 



It will be observed that we are dealing here with rather a 

 special case, viz., that of nourishment alone. Somatic cells 

 and body- cells alike are affected in the same way. If along 

 with this condition of nourishment there are certain correlated 

 changes, such as the formation of accessory carpels, the prin- 

 ciple remains the same. The point of special interest is that 

 the effects may be accumulated only slowly by the seeds, so 

 that it takes several generations to produce the best average 

 effects. The effect, once produced, may persist in part through 

 several generations subjected to the reverse conditions. The 

 results are not unlike those in the butterflies, in which the effects 

 of temperature or of feeding are marked in the first generation, 

 and then decline if the external conditions that produced them 

 are changed. 



It is difficult to reach any probable conclusion from the evi- 

 dence given in the preceding pages in regard to the inherited 

 effects of the influence of the environment. Possibly we are 

 dealing with two distinct problems. In most cases the effects 

 on the body-cells and on the germ-cells are only temporary, 

 and persist only as long as, or a little longer than, do the condi- 



