104 
J. C. Th. Uphof. 
One is able to arrange various xerophytic species, collected in 
different dry countries in three distinct physiological groups, as 
follows. 
Group I. Plants with vertical leaves, all of the same size 
and shape. The apex of each leaf ends in a long awn containing 
no chloroplasts. The anatomical construction of stem and leaves 
is decidedly sclerotic. Species belonging to this group all belong 
to the sub-genus Homceophyllum , e.g., 5. rupestris, (L.) Spring, 
growing in rocky places of the northern and southern temperate 
zone of the Old and New World; S. rupincola , Underw. on rocks in 
south-western United States and Mexico; 5. Watsoni , Underw. 
from the mountains of Utah and California ; S. Bigelowii Underw. 
reported from California; 5. extensa, Underw. collected from 
Las Candas, Luis Potosi, Mexico; 5. Underwoodii Hieron. 
from New Mexico; «S\ densa Rydl. from various parts of the 
Rocky Mountain States; S. mutica, D. C. Eaton, on cliffs in 
mountains of Colorado, Arizona and New Mexico; S. Ridellii 
van Es. from central and eastern Texas and probably also in 
southern Louisiana ; S. humifusd , van Es. growing on dry sandy soils 
in central and south Florida ; S. funiformis, van Es. frgm the sand 
dunes and barrens of Florida; 5. tortipila, A. Br. from South 
Carolina, growing on granite rocks in the mountains ; 5. Sherwoodii, 
Underw. growing on rocky places in North Carolina; 5. 
acanthonota, Underw. growing on sand barrens in Florida, Georgia 
and North Carolina ; 5. arenicola , Underw. on dry sandy ground 
and rock waste of central and north Georgia and Florida; 5. 
caffrorum , Hieron. and S. capensis , Hieron. reported from dry 
places in South Africa; S. Mildei, Hieron. from similar places in 
the province San Luis, Argentine ; 5. Sellowii , Hieron. from S. 
Diego, Brazil. There are further some other species belonging to 
this group, most of them being segregated from 5. rupestris , of 
which many have been described by Hieronymus, Underwood (26),# 
and Van Eseltine (8). 
Group II. Plants having slender, wiry, trailing stems, 
spreading over the ground, or hanging down from rocks or some¬ 
times from trees; the foliage consisting of two rows of dorsal and 
two rows of ventral leaves; the size of leaves being very much 
alike, although the shape may differ. Leaves of some species fold 
themselves round the stem when dry; certain forms have a slight 
resemblance to the last group ; e.g., 5. sanguinolenta, Spring from 
