8 
EDMUND W. SINNOTT AND IRVING W. BAILEY 
half of the pinnate simple leaves, on the contrary, are connected with 
a unilacunar nodal type. In fact, the great majority of unilacunar 
plants have simple pinnate leaves. Of the 5,080 unilacunar species 
in the floras studied, 4,430, or 87 per cent, are characterized by foliage 
of this type. The pinnate-lobed type is too infrequent among woody 
plants to make figures derived from it of any significance. This corre- 
lation between venation and nodal topography is not surprising, since 
the single bundle of the unilacunar node would naturally tend to con- 
tinue as a strong midrib (fig. 85), and the isolated traces of the multi- 
lacunar type would readily remain isolated and produce a palmate or 
compound lamina (fig. 84). In fact, the three lobes of a lobed leaf and 
the three leaflets of a trifoliately compound one are definitely related 
in their ontogeny to the point of origin of the three traces. 
The definite association of the unilacunar type (which seems 
clearly not to be primitive) with the simple pinnate leaf certainly 
indicates that this leaf type, now so dominant among Angiosperms, 
is not at all the most ancient one. The many cases where a multi- 
lacunar node, also, is present with this foliar form are to be regarded 
on such a view as the persistence of an ancient character at the node 
when it has been lost elsewhere in the leaf. 
2. Floral Parts. — The structure of certain supposedly conservative 
regions other than the node also furnishes evidence for the solution 
of our problem. One of these regions is the floral axis and its appen- 
dages. It is very noticeable that sepals, petals and floral bracts 
are often palmate in their venation when foliage leaves are otherwise. 
The homologies of the first two organs are still matters for debate, 
but bracts, at least, are almost certainly to be regarded as the morpho- 
logical equivalents of leaves. A few cases of palmation in floral 
structures are shown in figures 25 to 36. Of course there are many 
instances of pinnate sepals, petals and bracts but these are very rare 
in families where the leaves are typically palmate; and palmate floral 
parts are very frequent in plants with pinnate leaves. The wide- 
spread occurrence of palmation in floral parts may be looked upon as 
the persistence of an ancient character which has often been lost 
elsewhere. 
3. The Seedling. — The truth of the doctrine of recapitulation in 
its application to plants is frequently questioned at the present 
time but enough cases of conservatism in the seedling have been 
recorded to make evidence from this source worth seeking in any 
