Genus Polygonum. 233 
Further subdivision generally takes place in the glandular portion 
as this reaches maturity ; the walls are usually vertical but sometimes 
horizontal or inclined. Further subdivision of the stalk and basal cells 
is not infrequent, but does not take place to the same extent as in the 
secretory region. 
In all the species enumerated, and in others not bearing extra-floral 
nectaries, isolated glands which secrete gum occur upon the ochrea, 
petioles, stems, and leaf-blades (PL XVI, Fig. 5,^). 
The structure of these glands is in all essentials identical with that of 
the nectary-units just described (see Text-fig. 2). 
They arise as epidermal papillae, and follow the same course of 
F ig. 4. Gland from ochrea of Polygonum sachalinense . x 580. 
development as those of the nectary ; subdivision is however much less, 
and practically confined to the secretory portion. 
These, like the foregoing, function long before the leaf unrolls, and 
mostly fall off before the organs reach maturity. 
It is interesting to note in this connexion that similar glands secreting 
a mucilagenous substance and probably functioning as hydathodes have 
been described by Areschoug ( 1 ) on leaves of various species of Mangroves. 
II. Special. 
Polygonum cilinodum (Pl. XVI, Fig. 1). 
The nectaries in this species are circular in outline with a diameter 
of about 0-63 mm. They are saucer-shaped depressions surrounded by 
a well-marked lip, which slightly overhangs the concavity. 
