STEREOSPERMUM 
59 6 
Stereospermum Cham. Bignoniaceae (n). 12 sp. trop. Afr. As. 
Stembergia Waldst. et Kit. Amaryllidaceae (1). 12 sp. Medit. 
Stevia Cav. Compositae (11). 100 sp. trop. and subtrop. Am. 
Stifftia Mikan (Augusta Leandr.). Compositae (xn). 4 sp. Brazil. 
Shrubs. 
Stillingia Linn. Euphorbiaceae (A. 11. 7). 15 sp. Am., Polynes. 
Mascarenes. [For S. sebifera Michx. see Sapium. ] 
Stipa Linn. Gramineae (vm). 100 sp. trop. and temp., usually xero- 
phytes. A. pennata L., the feather grass of the Steppes, and many 
others have leaves which roll inwards when the air is dry, covering up 
the stomata and green tissue (which are on the upper side only) and 
exposing only the woody lower surface to the atmosphere. The awn 
of the fruit is very long, ending in a long feather. It is hygroscopic, 
curling up when dry and uncurling when damp. The fruit is thin and 
sharply pointed, with backward-pointing hairs on the tip. As in 
Erodium, the awn when damped uncurls, and, if the point of the fruit 
be on the soil and the feather be entangled with other objects, drives 
the fruit into the soil. When the air dries the feather is drawn down, 
not the fruit upwards. S. tenacissima L. (N. Afr.) is the esparto 
grass, from which paper is extensively made. 
Stokesia L’Herit. Compositae (1). 1 sp. South-east U.S. 
Stratiotes Linn. Hydrocharitaceae. 1 sp., S. aloidss L. (water soldier), 
Eur. (incl. Brit.). It has a short stem bearing roots and a number of 
aloe-like leaves with toothed edges. In the summer it floats up to 
the surface and bears the (dioecious) firs. It then sinks again, and 
once more comes up in August or later. Whilst down it gives off 
numerous axillary shoots with big buds at the ends, and when it floats 
again these grow into young plants, which soon become free and sink 
to the bottom, where they remain over the winter. [See p. 158.] 
Strelitsia (Banks) Ait. Musaceae. 5 sp. Afr. S. augusta Thunb. 
and S. Reginae Banks are often grown in hothouses. Firs, in a cin- 
cinnus in the axil of a large spathe. Sepals free ; the lateral petals 
united, irregular, enclosing the 5 sta. Fertilised by birds (Ber, D. 
Bot. Ges. 1894, p. 53). 
Streptanthus Nutt. Cruciferae (1. 1). 22 sp. Pacific N. Am. 
Streptocarpus Lindl. Gesneriaceae (1). 30 sp. Afr. The life-history 
is peculiar. In S. polyanthus Hook, (see Hielscher, in Cohn’s Beitr . 
z. Biol . d. PJl ., vol. Hi) the embryo in the exalbuminous seed has 
1 cotyledons and a hypocotyl, but no plumule or radicle ; the hypocotyl 
enters the soil, swells up at the end and developes absorbent hairs; 
presently however roots (adventitious) form above the swelling, which 
dies off. In the meanwhile one of the cotyledons continues to grow, 
while the other dies. Thus the young plant presently consists of a 
large green cotyledon with few adventitious roots. The cotyledon 
continues to grow, and reaches a considerable size. Finally the infl. 
arises as a bud from the base of the petiole, and leafy shoots may also 
