DEVELOPMENT AND DISTRIBUTION OF LEGUMINOS2. 381 
the ventral suture always directed to the dorsal aspect of 
the flower. Oarpel unilocular and bearing ovules in either 
one or two rows on the ventral suture. Fruit, a pod or 
drupe. Seeds rarely albuminous. 
The Differentiation of Leguminose. 
The ancestral forms of the legumes were such as to 
suggest great differentiation of the dicotyledons before the 
existence of the Order under consideration. 
Several interesting inferences are suggested by the 
analysis supplied in the previous chapter. Thus the geo- 
graphical distribution of the Leguminosz indicates a much 
greater age for the Papilionacesze than for either Ceesal- 
pinieze or Mimosez, while on the other hand, the corolla 
of Papilionacee is plainly aberrant in type, and of much 
more recent origin than the corolla of the ancestral form 
or forms. So also the leaves of Papilionacez suggest a 
much greater age for this family than the leaves of the 
Ceesalpinieee and Mimoseze suggest for these families, 
nevertheless the stamens of Papilionaceze stamp it as an 
aberrant family among the legumes with the exception of 
Sophoreee. From every viewpoint the Papilionaceze appear 
to be a family much younger than the early forms of the 
legumes, nevertheless one which by its adaptability has 
outstripped all its allies in occupying the globe. Cesal- 
pinieze and Mimosez are less elastic types which represent 
modifications of the ancestral forms mainly within the 
limits of the tropics and subtropics. It is perhaps legitimate 
to consider that the irregular flower of Papilionacez arose 
as an adaptation to fertilisation by insects. In Cesal- 
piniez, again, may be noted a slight amount of irregularity 
in the flower, nevertheless the estivation is imbricate and 
ascending in this family, but descending and imbricate in 
Papilionacez, and the standard is outside in the latter but 
enclosed in Ceesalpinieze. The pinnate leaves of Mimosez, 
