EXPERIMENT STATION REPORT. 265 



The accompanying diagram shows graphically, by the solid 

 line, the distribution of the 507 heads among the ray numbers 

 from 7 to 26, the single instance of a 32-rayed and a 42-rayed 

 head being omitted. By means of the fine dotted line is shown 

 the curve constructed for the terminal heads, and the bars and 

 dots indicate the curve for the fifth to the ninth lateral heads, 

 all three curves from the deduced basis of 507 instances. 



The Effect oe a Midsummer Drought upon Ligneous 



Plants. 



The growing season of 191 o was unusual in that there was a 

 prolonged drought in July and August followed by copious 

 rains. So dry w'as it that many of the various truck crops were 

 materially shortened as, for example, sweet corn and summer 

 squashes noted elsewhere in this report. 



In connection with the checking of vegetation in midsummer,, 

 some observations have been made upon the foliage and young: 

 stems of several trees and shrubs. Ligneous plants upon dry 

 knolls naturally have yielded interesting results far in excess of 

 those that grow in lowlands or along streams and ponds that 

 have a constant subterranean source of water. 



As a preliminary, it may be stated that plants generally have 

 the first leaves somewhat smaller and often of different shape 

 from those that are produced later upon the same branch. 

 There seem to be evident reasons for this as these leaves were 

 started in a bud that was preparing for a period of rest (winter) 

 and that finally has its exterior made up of specialized leaves 

 that have their service in protecting the delicate parts within, 

 A minimum of food combined with a degree of confinement may 

 be sufficient to account for the lack of size and any special shape 

 of the first leaves. Furthermore, there is a demand for small 

 leaves quickly formed to prepare food for the shoot that later 

 will bear larger leaves which in turn place the smaller, earlier 

 make-shifts, so-to-say, literally in the shade. As a matter of 

 fact, twigs that have attained to the full stature of mid-season 

 growth generally have dropped their first formed leaves for they 

 have passed the period of their usefulness. 



A quite limited study of the early leaves, together with meas- 

 urements, leads one to the opinion that the short broad type is- 

 to be associated with that of the early development of the bud 

 from its resting condition, while a longer and narrower form is 

 associated with that of the mid-season when the growing twig- 

 has its terminal bud free from all incumbrances of bud-scales 



