374 
E PJ MEDIUM 
pendulous, with glandular hairs on the stalk. It is protogynous, and 
after a time the valves of the anthers bend upwards and roof over the 
stigma, and the male stage begins. Finally self-pollination occurs by 
the elongation of the style carrying the stigma among the valves. 
The nectaries are of a curious shoe-like pattern. The seeds have 
a membranous aril. 
Epipactis Adans. Orchidaceae (4). 10 sp. N. temp.; 2 in Brit., E. lati- 
folta All., and E. palustris Crantz (helleborine). There are two 
staminodes at the sides of the column ; the anther is acrotonic. The 
labellum has a hinged terminal portion, which by its rebound causes 
the insect to fly somewhat upwards in leaving the fir. In so doing it 
rubs the rostellum, which instantly becomes very viscid and cements 
the pollinia (which have no true caudicles) to the insect. The chief 
visitors are wasps (p. 92). See Darwin’s Orchids , p. 93. 
Epiphyllum Haw. Cactaceae (1. 1). 4 sp. Brazil, often epiphytic. 
Epipogum S. G. Gmel. Orchidaceae (4). 1 sp. Eur. (incl. Brit.), As., 
E. aphyllum Sw. a leafless saprophyte (p. 177) with a branched 
rhizome and no roots ; it has an endotropic mycorhiza (p. 39). Fir. 
as in Epipactis, but without any twisting of the receptacle. 
Epipremnum Schott. Araceae (11). 8 sp. Indo-mal. 
Epirrhizantlies Blume=Salomonia Lour. 
Episcia Mart. Gesneriaceae (1). 30 sp. trop. Am. 
Epithema Blume. Gesneriaceae (1). 10 sp. Indo-mal., trop. Afr. 
Equisetaceae. Pteridophyta (Equisetineae). An order with only one 
surviving genus (Equisetum, q.v .), but formerly well represented upon 
the earth. Many large fossil forms (Calamites, &c.) are known. 
Equisetineae. One of the main divisions of Pteridophyta (q.v.), con- 
taining the single order Equisetaceae. 
Equisetum Linn. Equisetaceae (the only genus). 25 sp. temp, and 
arctic ; 9 in Brit, (horsetails), chiefly in swampy places. They are 
perennial herbs with sympodial rhizomes, which send up aerial shoots 
each year. These may be of one or two kinds ; in some sp. the 
ordinary green shoot bears the reproductive spike at the end, while in 
others there is a special reproductive shoot, usually appearing early 
in the year, and often without chlorophyll, the ordinary shoots per- 
forming assimilating work only. The stem is very distinctly jointed, 
and at the nodes are borne whorls of united leaves, closely pressed 
against the stem, and of little or no use in assimilation. The branches 
emerge through the leaf-sheath and thus appear at first sight endo- 
genous in origin (p. 38) ; in reality they are exogenous, but formed 
so much later than the leaves that their points of origin are already 
covered by the leaf-sheath, and so they are compelled to burrow 
through it. Stages in this process may easily be observed. The 
surface of the stem is grooved; the ridges are occupied by mechanical 
tissue, whilst the green tissue and stomata are at the base of the 
furrows. This is a marked xerophytic structure (p. 166) and is 
