No. 429.] FOLIAGE IN THE GENUS ACACIA. 729 
In the case of the A. /eprosa seedlings with abnormal devel- 
opment the lateral pinnae may be regarded as further modifica- 
tions of the proximal pair of leaflets of the ordinary first leaf of 
seedlings.! If this is, as seems probable, the right interpreta- 
tion of such peculiar forms, it almost necessarily follows that 
the change in all the species at this stage is of the same nature, 
and that as a rule the higher, or more distal, leaflets upon the 
main axis lose the power to develop, on account of the greater 
strength of the newly developed 
lateral pinnz. It may be worth 
while to state that these stages 
were found only after their predic- 
tion as the result of a course of 
reasoning, and were the direct 
objects of the search which led to 
their discovery. 
The tendency toward triple pin- 
nation is likewise, as may be easily 
seen by reference to the figure, 
only present upon the proximal 
leaflets of the pinnz, and not at 
all to be found on the pinnz near 
the tip of the leaf. 
The final point to be discussed 
is the gradual metamorphosis to 
the phyllode. In seedlings where ; leanai im) 
the change is gradual, as is the 
case in the great majority of species, but one pair of pinnæ 
is present at the time of its occurrence. In the abnormal 
seedlings shown, the prolongation of the axis is suppressed 
as the transition stages appear. In such cases it is possible to 
say with a high degree of certainty that the phyllode represents 
merely the flattened petiole. Next to be considered are the 
conditions of such forms as experience these changes later 
in life. 4. rubida A. Cunn. and A. heterophylla Willd. have 
already been described by Reinke, and in his article one stage 
in the transition as it occurs in A. heterophylla is figured. 

Fic. 2. — Abnormal seedling of A . Zeprosa 

! Cf. seedling of Gleditsia, where such transition stages are frequent. 
