3i8 
EDMUND W. SINNOTT 
Sarcocephalus where the presumably ancient trilacunar condition 
persists. 
CUCURBITALES 
The Cucurbitaceae are entirely trilacunar, apparently. The 
petiole in most members of the family is large, especially at the base, 
and contains a ring of many strands. Just as these enter the stem, 
however, they become grouped into three bundles, each of which is 
inserted separately. 
Campanulatae 
In this order the Campanulaceae are entirely unilacunar. The 
Goodeniaceae and Compositae, however, are trilacunar {fig. 28) or 
in rather rare cases multilacunar. The theory so generally held and 
maintained in the recent classifications of Engler and Hallier that the 
Compositae have been derived from the Campanulaceae or their near 
allies therefore receives no support from nodal anatomy "for if our 
general hypothesis as to the origin of the different types of nodal 
structure in the angiosperms is correct, we should certainly not expect 
the trilacunar condition of the Compositae to have been derived from 
the unilacunar (and hence reduced) one which characterizes the Cam- 
panulaceae. We should more naturally look to the trilacunar Goodeni- 
aceae, Dipsacaceae or Caprifoliaceae for the ancestors of the Com- 
positae. Evidence from nodal anatomy seems to indicate that the 
Campanulatae ought perhaps to be divided into more than one order. 
The following table presents a more condensed summary of the 
occurrence of the various types of nodal anatomy throughout the 
dicotyledons. Numbers refer to number of gaps. Those in paren- 
thesis indicate rare conditions for the family. 
This tabular review of the nodal anatomy of the dicotyledons 
makes it evident that we are here dealing with a character which is 
almost always very constant within any particular family. It will 
be noted that a trilacunar condition may frequently become expanded 
into a multilacunar one in the same family or even in the same genus, 
but that it is rarely contracted into the unilacunar condition in nearly 
related forms. The two main types are really the unilacunar and the 
multilacunar and it is only in comparatively few cases, such as the 
Magnoliaceae, Cruciferae and Dilleniaceae that these both occur in 
any considerable number in the same family. 
