Briggs and Johnson, Hopkinsiaceae and Lyginiaceae 
485 
The arrangement of axes, especially after flowers have fallen, may suggest sympodial 
growth but we interpret tire inflorescence structures as not sympodial. Flowers are not 
in spikelets; flowers or flower-clusters are in the axils of small, ovate, acute, hyaline 
bracts at two or several closely-spaced uppermost nodes of the culms and the lateral 
branches. Male inflorescences bear clusters of several flowers on short slender axes; 
female inflorescences are similar but bear a single flower in such a position. Both male 
and female inflorescences are terminated by very small abortive axes (at the base of 
the uppermost flower) bearing minute bracts. Male and female flowers are described 
above for the family. 
Pollen and embryology: the pollen grains are spheroidal to oblate, ulcerate, with a 
polar diameter of 24-28(-33) pm. (Chanda 1966; Ladd 1977). The pollen walls show a 
well-developed foot-layer, columellate interstitium, and a well developed tectum, 
with numerous pores ('scrobiculi') penetrating the tectum and the foot-layer, as well 
as other pores ('puncta') that penetrate the tectum only. Tire pollen surface shows 
micro-verrucate ornamentation. The aperture is of graminoid type (Linder & Ferguson 
1985), the annulus with a heavily thickened foot-layer, and the aperture diameter less 
than 3-4 pm. A thin layer of endexine covers the ulcus and extends some distance 
under the margins. The endothecium of the anthers contains spiral thickenings that 
are distinctive in forming perfect helices that are doubled (Manning & Linder 1990). 
The integuments are impregnated with tannins and the nucellar epidennis consists of 
isodiametric cells (Kellogg & Linder 1995); the small, densely packed cortical cells of 
the ovary resemble those of Lyginia (Linder 1992). The stigmas are dry. Embryo 
development has not been studied. 
Karyology: only a count of 2 n = 18 for H. adscendens, here published, is available. 
(Fig. 3). 
Fruit, seed and reproductive biology: flowers are wind-pollinated; the pollen is 
released explosively and is normally completely expelled from the anther. The 
dispersal unit is the fruit; a small drupe with thin fleshy pericarp, shed with a short 
stout fleshy pedicel that contains oil and presumably functions as an elaeiosome. The 
testa is fused to the pericarp, but with a white layer that may be equivalent to the seed 
coat of related groups such as Lyginiaceae. Germination is hypogeal with the 
I-1 
Fig. 3. Hopkinsia adscendens, mitotic metaphase, 2 n = 18 (prepared as in Briggs 1966); voucher: Briggs 
358. Scale bar = 5 pm. 
