105 



about twice as long as broad, oval in outline, with an obtuse tip, 

 the base of the blade acute and commencing at opposite points 

 on the petiole. 



There remains now to be considered the characters of the 

 venation. In all sassafras leaves, the midvein extends from the 

 base as a petiole. In some bud leaves the parenchyma of the 

 blade continues as a wing-like appendage along each side of the 

 midvein to the point of attachment. As the leaves become older 

 this appendage is not found, and the petiole is channeled. 



Upward the midvein passes to the tip of the leaf, sometimes 

 forming a short, sharp projection, sometimes a cusp. At times, 

 the parenchyma extends beyond the end of the midvein, forming 



Figure 4. 

 Acute type of base. 



Figure 5. 

 Wedge type of base. 



Figure 6. 

 Rounded type of base. 



an emarginate tip. This is probably due to an arrestation of the 

 growth of the midvein, while the parenchyma on either side con- 

 tinues to grow. 



From the midvein a number of secondaries are given off. 

 As these soon curve upward and loop into the next succeeding 

 vein, the nervation may be described as pinnate-camptodrome. 

 Two large secondaries always branch off from the midvein near 

 its base. The disposition of these is not the same in all leaves. 

 Sometimes they are opposite, while at other times they are not. 

 Of the five hundred leaves examined 18.8 percent, were oppo- 

 site and the remaining 81.2 per cent, were not. It may be remem- 

 bered in this connection that the majority of the bases of the leaf 



