EXPERIMENT STATION Ri-LPORT. 269 



neighborhood of the fifth internode. On the other hand, the 

 internodes of the resumed growth equally uniformly increase in 

 length toward the growing tip until the normal is attained. 



It is also determined that there is an absolute shortening of 

 the petiole at the center of the disturbed area and an increase 

 both up and down the stem. Relatively the petioles were not 

 shortened when they are considered in connection with the size 

 of the blades they bore. 



The length and width measurements do not state accurateh^ 

 the areas of leaves but are convenient terms of comparison. 

 From the tables, it is gathered that the foliage is checked more 

 in length than in width growth. 



Leap Variation. 



When one is studying the variations in vegetable-fruits, as 

 the beans, eggplants, peppers, squashes and tomatoes, it is quite 

 to the purpose to keep in mental touch with the forms that are 

 exhibited by other plants that are either wild or being grown 

 under widely differing conditions from those obtaining in the 

 garden. 



Below is a brief and incomplete record of some wayside 

 studies of two acknowledged weeds, one indifferent plant of the 

 pastures, and lastly an ornamental shrub that was close at hand. 



LEAVES OE RAGWEEDS. 



The Ragweed (Ambrosia arteinisiacfolia L.) has handsome 

 finely divided leaves and upon the same plant they are usually 

 quite uniformly alike, so that one might well conclude that the 

 foliage of this species exhibited no marked variation. But when 

 one studies these plants, one with others as they grow in dis- 

 couragingly large numbers almost everywhere, is is soon ap- 

 parent that the variations are great. Thus, as a whole, some 

 leaves are long and slender while others are broad and tri- 

 angular. Very many have the tips of the many lobes broad 

 and blunt (Plate XXII, i), while others are acute (2 and 3). 

 A study of a few of the numerous forms given in Plate XXII 

 will serve to introduce the reader to the subject of leaf varia- 

 tion among the plants of the same species, as abundantly illus- 

 trated in a common wayside weed. 



In Ambrosia trifida L., the "Great Ragweed," one finds the 

 variation great upon the same branch, as illustrated in the set 

 shown in the lower portion of plate XXII. The first leaves (4 ) 

 here are of a verj- simple type, namely, oval-serrate ; but shortly 



