268 NEW JERSEY AGRICULTURAL COLLEGE. 



compound type bein<; quite common among the larger leaves 

 situated, as a rule, in the more central portion of the year's 

 wrowth. In the twig shown, there are three pairs of these com- 

 pound leaves upon nearly equidistant nodes. The checked 

 growth is recorded in the succeeding shorter internode and the 

 pair of small leaves, one of them entirely simple and the other 

 Avith the side leaflets greatly reduced. From this cessation point 

 the internodes increase in length for a time. The leaves had 

 fallen from two nodes (6), due to the unfavorable conditions 

 induced — leaves that approach somewhat the nature of bud- 

 scales are often short-lived — but the third pair is intact and 

 each leaf show^s an oval form, an entire margin, a slightly refuse 

 tip. very different from the leaves below and above them. In 

 many of the stems of this Forsythia, the compound leaves were 

 (leveloped after the rest period and apparently the full vigor of 

 two months or so earlier had been restored. The size and 

 complexity of a leaf in any given species like this one becomes 

 an expression for conditions of growth, one always being mind- 

 ful that internal forces play no negligible role in determining 

 the size and form of the various parts and therefore under iden- 

 tical conditions plants of the same kind do not express the same 

 results. 



At 7 is a spray of English Ivy (Hcdera Helix L. ) in which 

 the cessation zone is evident from the shorter internodes and 

 the smaller leaves. Here the dwarfed leaves (8) are very broad 

 without evident petioles followed by leaves with outline far less 

 irregular than in the normal leaves on their long petioles shown 

 below and above this zone. 



So far as time would permit, this study of the effect of the 

 midsummer drought has been extended into the nursery, or- 

 chard and forest with the result that whatever has been stated 

 above and shown in the engraving is of general application. 



In short, when hard times come on more or less gradually 

 like the drought in question, plants are naturally checked in their 

 growth and it is permanently recorded in ligneous plants in the 

 shortened internodes even to the less enduring bud-scale scars, 

 and for the passing season in simplified leaves that approach the 

 type of the first upon a new branch and peculiar to the species 

 in cjuestion. 



It is drawn from the tables of measurements of sets of stems 

 with their leaves that the last leaf formed before the temporary 

 cessation has the shortest internode below it of any affected by 

 the drought. Furthermore, the internodes below the shortest 

 in regular order are longer until the normal is reached in the 



