RO CGASS-BOOK OF BOTANY. 
CHAPTER V. 
Hirasertro the flowers which have been examined and de- 
scribed have possessed (with a few exceptions) a double 
perianth, readily distinguishable into calyx and _ corolla. 
Those to be described in this chapter are usually furnished 
with a single perianth, or are destitute of any floral envelope, 
In those cases where the perianth is double it is not distin- 
cuishable into calyx and corolla, all the leaves, as a rule, being 
of similar structure. 
21. Dock (Rumex obtustfolius and fi. crispus), 
Two or three kinds of Dock are common in New Zealand, 
but probably the two named are the most abundant. There 
are also two native species, one of them—J. flexwosus— 
which has tough much-branched prostrate stems and 
narrow leaves, being very common. 
In all docks the leaves are revolute* in vernation|— 
that is to say, their margins are rolled outwards before they 
expand (the term vernation being applied to the mode of fold- 
ing of leaves in the bud). The leaves are furnished with very 
characteristic stipules called ochrez,} which, instead of 
- being placed at the sides of the petiole like wings, form a sort 
of sheath to the stem above the attachment of the petiole. 
These ochrez are usually of very thin scarious texture. 
The small green flowers are crowded into panicles which 
are arranged in whorls in the upper portions of the branches. 
Each flower has a perianth of 6 leaves arranged in two whorls, 
the inner three of which in RB. obtusifolius have strongly- 
toothed margins, while in R. crispus they are nearly entire. 
They are generally furnished on the midrib with a swollen 
knob or tubercle. There are 6 stamens, and a 1-celled, 
sharply-3-angled (triquetrous§) ovary. From the apex of 
the latter, and projecting over each of its angles, is a slender 
style, bearing a flattened and feathery stigma. In longl- 
rea section the ovary is found to contain a single erect 
oyule. 
oo fee 
* Lat. re, back; volwo, I roll. 
t Lat. ver, spring, hence vernatio. 
} Lat. ocrea, a covering to protect the legs. 
§ Lat, triquetrus, three-sided. 
