Two queries

[Jane Browning]

Research has shown that plants of Bolboschoenus (previously
Scirpus)(Cyperaceae) from fresh water localities carry spikelets with
glumes paler in colour than those of the same species from nearby
coastal (brackish) habitats. This has been reported in America and
for Eurasia (Koyama, 1962: 932), and in South Africa from my own
studies in an estuarine/riverine area. Is anyone prepared to offer an
explanation of this? Is it known, perhaps, for cyperaceous genera
other than Bolboschoenus?
A second query concerns achene conformation.
In Bolboschoenus, achenes 2--4 mm long x 1--2 mm wide serve as a food
source for migratory and permanently resident birds. Within a species
of Bolboschoenus, for example B. maritimus, are populations in which
biconvex (lenticular) achenes predominate, as opposed to others in
which trigonous (three-angled) achenes are the more frequent. Is
there any information on selective forces that might favour either of
these achene types? Apart from shape in cross-section, there appear
to be no other marked differences in the achenes.

Jane Browning
E-mail=browning at botany.unp.ac.za