No. 429.] FOLIAGE IN THE GENUS ACACIA. 733 
data in support of a principle dealing with a progression. On 
the whole, the conditions of the seedlings of A. /eprosa and of 
the leaf of A. decurrens stand strongly in favor of the existence 

Fic. 6. Fic. 7. 

Fic. 8, FIG. 9. 
Fics. 6-10. — A . heterophylla, variations in transition to phyllode. (l!4natural size. 
of a regularly increasing complexity in leaf form, governed 
by fixed laws and repeated in an abbreviated form in plant 
ontogeny. To a certain extent also they add weight to Professor 
