DICOTYLEDONS 217 
SUMMARY 
Owing to the enormous number of Dicotyledons the 
task of arranging them systematically is a formidable 
one, and it is unlikely that any arrangement yet pro- 
posed can be considered final. Very much more infor- 
mation is needed in regard to the development of both 
floral and vegetative parts, as well as in regard to the 
embryology, especially in the obscure and doubtful types, 
before we shall have the data necessary for a satisfactory 
classification. Their relation to the Monocotyledons is 
also very uncertain, and a thorough comparison of the 
lower types of Dicotyledons with these is very much 
needed. 
Itis generally admitted that the apocarpous Choripet- 
ale, t.e. those with entirely distinct carpels, are the most 
primitive. The simpler Ranunculacez offer many resem- 
blances to the apocarpous Monocotyledons, and it is possi- 
ble that here we have a point of contact between the two 
groups. It is, however, not at all impossible that the 
Dicotyledons have had a multiple origin, and the possi- 
bility of the derivation of the Piperinez, and possibly the 
lower Centrosperme from monocotyledonous types like 
the aroids, is not improbable. This would imply that 
some, at least, of the apetalous Dicotyledons are prim- 
itive types, and not reduced from petaloideous forms. 
The occurrence of numerous apetalous types among the 
oldest fossil remains of Dicotyledons also strongly sug- 
gests their primitive character. If this view is correct, 
it is quite possible that the Amentaceze and some other 
Apetale constitute a line of development entirely dis- 
tinct from that of the petaloideous forms. 
