Bracts in Welwitschia mirahilis. 
549 
are present, and starch is produced in these, as in the case of the epidermal 
cells of the leaf and stem in Ephedra. 
The Stoma. The presence of stomata in the bracts has been noted 
by Hooker , 1 Strasburger , 2 and Sykes . 3 Stomata occur in all kinds of 
bract. They are not so deeply sunken as in the adult leaf, but not so super- 
ficial as delineated by Sykes (Figs. 3-4). The guard-cells are much the 
same as those of the cotyledon in shape and structure. The ventral wall 
consists of cellulose, and the upper portion of the dorsal wall is thickened 
and slightly lignified, not giving a strong reaction to phloroglucin or aniline 
sulphate. 
Stomata are distributed in the exposed parts of the bracts, except near 
the margin, and are generally longitudinally and only rarely obliquely 
Text-Fig. i. A portion of the epidermal cell from the exposed part of the male cone- scale 
in surface view, x 285. 
orientated. The mode of their development is exactly the same as in the 
case of the leaf and cotyledon 4 (Text-fig. 1). 
The Mesophyll. The exposed portion of the bract is considerably 
thickened, and consists, in the case of the male cone, of about six cells, and 
in the case of the female cone, of more than ten cells in thickness . 5 In the 
fully developed bracts of all kinds, palisade tissue is present under the outer 
epidermis. This tissue is perhaps best developed in the male cone-bract 
and consists of one or sometimes two layers of cells. In the female cone- 
bract this tissue is greatly interrupted by the presence of spicular cells. 
Sykes 6 did not observe any palisade ; she appears to have not recognized 
that she was dealing with immature structures. The spongy parenchyma 
cells are roundish and contain chloroplasts. In the wall of these cells of full- 
1 1. c., p. 25. 2 1. c. (1), p. 94. s l.c., p.185. 
4 Cf. Takeda, H., 1. c., p. 351. 5 Strasburger, E., 1. c. (1), p. 94. 6 1. c., p. 185. 
P p 3 
