Upright cells, however, are more common in rays of such species as Cheiranthus mutabilis and Stanleya pinnata (Fig.
Within Brassicaceae, the longest vessel element lengths occur in the species with the most mesic habitat, Cheiranthus mutabilis, from Madeiran laurel forest openings (Carlquist, 1971).
Perennials that deliver lots of showy blooms in spring and summer without copious amounts of water include bougainvillea 'Crimson Jewel', gaillardia (pictured at left), erysimum (also sold as Cheiranthus
'Mauve clusters'), lavender, garden penstemon, salvia superba 'East Friesland', and yarrow.
Polyanthus and wallflowers are reliable as are winter flowering pansies while the Siberian wallflower, cheiranthus
, is useful as you can cut it back hard after flowering and it will bloom again in summer.
He originally ascribed the preferential production of outcrossed progeny in Cheiranthus to differential pollen-tube growth in the style, but selective abortion of selfed seeds caused by inbreeding depression also increases the frequency of outcrossing in self-compatible species (Moran and Brown 1980; Levin 1984; Cheliak et al.
Differential pollen-tube growth was invoked by Bateman as the mechanism for the preferential production of outcrossed seed in Cheiranthus, but the possible contribution of selective ovule abortion was not excluded in his study or in several more recent reports (e.