142 



Descriptive Flora 



eventide and closing the following day. Petals 10. Stamens 

 many, of different lengths. Fruit a cylindrical, erect capsule 

 crowned by the 5 spreading sepals, rough like the leaves and 

 easily dispersed by fur-bearing animals. April to July. Dry, 

 limestone hills and rocky hillsides. Named for Mentzel, a Ger- 

 man botanist. (A similar plant with smaller leaves, weaRer 

 stems and flowers from y 2 to %" across is probably Mentzelia 

 oligospermia Nutt.) 



Mentzelia strictu Osterhaut. 

 Nuttallia striata (Osterhaut) Greene. 



Similar to Mentzelia nuda but petals are very pale yellow or 

 straw-colored. In the sandy region to the south and east of San 

 Antonio. 



LYTHRACEAE. Loosestrife Family. 



LytJirum lanceolatum Ell. Loosestrife. 



Slender stemmed, branching, leafy plants with bright purple 

 or violet flowers that blossom up the stem (one in the axil of 

 each leaf) as it lengthens. Leaves alternate, about 1 inch long, 

 linear to linear-elliptic, usually folded against the stem. Flowers 

 small, rose-purple to violet, about V2" across, in the axils of the 

 numerous stem leaves. Petals 4 to 6 (usually 6), together with 

 the sepals and stamens, united at their bases to a slender green, 

 ribbed tube called the hypanthium. Petals usually have a dark 

 purple mid nerve. Stamens usually 6, included in the tube. 

 Fruit a slender, conspicuously ribbed capsule less than 14" long, 

 and with 5 or 6 short teeth at the summit. April to July. In 

 open fields. 



OPUNTIACEAE. Cactus Family. 



Opuntia lindkeimeri Engelm. Prickly Pear. "Nopal". 



Cactus, 1 to 10 inches high, with large, usually vertical, flat, 

 conspicuously jointed stems, that m are generally mistaken for 

 leaves. Each leaf like joint is one foot or less long, and is well 



