Genus Polygonum. 231 
Winter buds upon their emergence in the spring have actively secreting 
nectaries upon bud-scales which possess no lamina. 
In only one species, viz. P. Convolvulus were seedlings obtained ; and 
these showed variations in the occurrence of the nectaries. 
In no case were they present upon the cotyledons, but whilst they 
appear to be normally present on the petiole of the first leaf, occasional 
specimens had no nectary till the second or third leaf was reached. 
The depressions forming the nectaries are lined with secretory trichomes 
which form a closely packed layer over the whole surface. The trichomes 
or unit structures of the nectary consist of three parts. 
The lowest or basal portion consists of large sac-like thin-walled cells, 
which with their neighbours form an almost continuous layer one cell deep, 
and for each gland number four or more in a single story (Text-fig. 2, b> on left). 
^IsUvcL Jrom 
Fig. 2. Nectary- and leaf-glands of Polygonum compactum. g. gland cells ; s. stalk cells ; 
b. basal cells. 
The middle layer is also one cell deep, and consists of flattened cells 
whose vertical walls are thickened, the horizontal walls — separating them on 
the one hand from the basal cells, and on the other from the gland cells — 
remain thin (Text-fig. 2, ^). 
The gland cells forming the third portion are usually not more than 
one cell deep, but may become subdivided by transverse walls ; they form 
an enlarged head of numerous cells elongated in the vertical direction and 
with comparatively thin walls (Text-fig. 2, g). This type of structure 
is frequent in secreting trichomes, and also finds its parallel in the hyda- 
thodes of Piperaceae, Bignoniaceae, and species of Artocarpus as was shown 
by Haberlandt (8, p. 420). 
As regards the cytological details, they are those characteristic for 
secretory cells in general ; the gland cells when young are completely 
