Several interesting members of the Morning-glory Family or Convolvulaceae are present on the outcrop. We found Convolvulus equitans, Gray Bindweed, everywhere. Its flowers are very small but beautifully detailed. They may be solid white or have a maroonish throat.
Evolvulus nuttallianus (= E. pilosus), Hairy Evolvulus, has tiny lavender-purple flowers that look like tiny Morning-glories. The leaves are silky-hairy on both sides.
Evolvulus sericeus (Silky Evolvulus), on the other hand, has leaves hairy only on one side. Its little flowers are white.
Dodder (Cuscuta) is a curious plant that is either a member of the Convolvulaceae or deserving of its own family--the Cuscutaceae. Dodders are parasites--they have no roots and no chlorophyll to make food of their own. They get their nourishment by tapping into the plants they grow over. Common names include Witches' Shoelaces and Love Vine. Texas species are often a bright orange in color.
Here we see the Dodder growing on an unfortunate individual of Verbena pumila or Pink Vervain. The close-up shows the flower shape characteristic of Verbena--nearly regular, but with three of the corolla lobes larger than the other two.
At about the same place, we found several very small specimens of Spermolepis echinata, Bristly Scaleseed. There are three species of Spermolepis in Texas. S. echinata is the only one whose fruits have hooked hairs. It's always helpful to have a microscope handy when examining members of the Carrot Family (Apiaceae)!
A microscope is also useful when trying to key a sample of Lesquerella (Bladderpod) to species. Many of the important characters belong to the tiny star-shaped hairs found on the leaves, stems, and/or fruits. If we have done our keying correctly, this is Lesquerella argyraea, the Silvery Bladderpod. Notice that even though the stems are thickly clothed with stellate hairs, the fruits are quite bald (glabrous).
The last plant on our tour of the side of the outcrop is a Milkweed, Asclepias asperula. Asclepias flowers are highly modified--the stamens and style are fused into a gynostegium. There is an extra perianth whorl, the corona, made up of hoods and horns. The pollen is produced in waxy masses called pollinia, which are connected in pairs by a gland and translator arms. The pollinator is usually a butterfly. The fruit will be a follicle full of seeds, each equipped with a fluffy parachute.
I need a lunch break on the Top of the
I want to go back to the Introduction