147 
The Pentacyclidce. 
three-fourths of the total number of species in the cohort. 
Isomery of the andrcecium is typical of the relatively large order 
Epacridaceae ; the stamens equal the petals in number also in the 
small degenerate order Lennoaceae; and in the Diapensiaceae, 
what may be an intermediate stage 1 is represented, in which an 
isomerous whorl of stamens alternates with an outer whorl of 
staminodes placed opposite to the petals. 
The gynaecium is multilocular, and usually multiovulate. In 
the bulk of the species the carpels are isomerous with the corolla ; 
in Clethraceae and Diapensiaceae the transitional number 3 
appears; but a bicarpellary ovary is a very rare occurrence in this 
cohort. Reduction in the number of ovules is traceable within the 
limits of the two largest orders, Ericaceae and Epacridaceae, and in 
Diapensiaceae. The larger of the two tribes in which Bentham 
and Hooker divide their Epacrideae is distinguished by the uniovulate 
condition of each loculus of the ovary; in Lennoaceae this condition 
is the invariable rule. 
From the foregoing statements it is clear that the tendency 
to economy in production of parts, so important a feature in the 
Archichlamydeae, is still actively at work in the Ericaies. The 
significance of this, particularly in regard to the linking of the 
Archichlamydeae with the Synipetalae, is emphasized by the 
retention of a polypetalous corolla in not a few species of this 
cohort; polypetaly characterizes the Clethraceae, most Pyrolaceae, 
some Ericaceae, and a few Epacridaceae. Correlated with this 
ancestral trait is the position of insertion of the stamens ; these 
are hypogynous in most of the species concerned, and free of the 
corolla, or adherent to its base only. In the Epacridaceae, however, 
the stamens are frequently epipetalous, either in the tube, or in 
some cases, at the throat of the corolla. 
As is to be expected, a cohort so actively occupied, so to speak, 
with the tendency to economy does not display in any high degree 
the general adaptations to insect visits which were summarized in 
the last chapter. The corolla tube, we have just seen, is not yet 
established as a perfectly constant feature, although sympetaly 
characterizes the large majority of the species. Conspicuousness is 
attained, speaking generally, by the aggregation of relatively small 
flowers into more or less dense clusters, spikes, &c.; and this, in 
some rare cases—notably in the Rhododendra—has been followed 
by Zygomorphy. 
1 But see infra p. 152, on the significance of staminodes. 
