416 
HYMENOPHYLLA CEAE 
3 gen. with 200 sp. trop. and temp. The filmy ferns are found chiefly 
in damp woods. Stem very slender, often creeping ; sometimes it 
bears roots, in other cases only root hairs. It grows more rapidly 
than the leaves, so that its leafless tip appears naked like a root. Leaves 
pinnate, filmy in texture (being only one cell thick, except at the veins), 
with no stomata. The placenta is at the leaf-edge, a continuation of 
the vein ; it bears sporangia and is surrounded by a cup-shaped indu- 
sium. Sporangia sessile, with oblique or transverse complete annulus, 
and opening by a longitudinal fissure. The prothalli are capable of 
long life ; in some sp. they produce gemmae or buds on the margin, 
and may thus multiply vegetatively to a considerable extent. Chitf 
genera: Hymenophyllum, Trichomanes. 
Hymenophyllum Linn. Hymenophyllaceae. Over 80 sp. trop. and 
temp. 2 in Brit, (filmy ferns), H. tunbridgense Sm. and H. Wilsoni 
Hook, moss-like plants growing in damp, shady places. 
Hymenophysa C. A. Mey. Cruciferae; position in the order doubtful. 
2 sp. Cent. As. See Nat. PJi. 
Hyophorbe Gaertn. Palmae (iv. 6). 3 sp. Mascarenes. 
Hyoscyamus (Tourn.) Linn. Solanaceae (11. 3). n sp. N. Afr., Eur., 
As. H. niger L. (henbane) is found in Brit., but probably is only an 
escape, it having formerly been largely cultivated as a narcotic. The 
firs, are in cincinni. The capsule stands erect enclosed in the calyx, 
and opens by a lid ; the seeds can thus only escape in strong winds, &c. 
Hyoseris Linn. Compositae (xm). 3 sp. Medit. 
Hypecoum Tourn. ex Linn. Papaveraceae (1). 12 sp. Medit., Cent. As. 
Fir. 2-merous throughout. The inner petals are 3-sect, and the middle 
lobe stands erect and encloses the sta. Eichler (Bliithendiag.) and 
others regard the androeceum as derived from the Fumaria type by 
union in pairs of the lateral branches of the outer whorl of sta., so as 
to form an apparent inner whorl of sta., but it is quite probable that 
the 2 inner sta. are really a true inner whorl. As in other cases, the 
evidence cuts both ways, and may be used as proof of the derivation 
of the Fumaria type from Hypecoum by splitting of the two inner 
sta. and the union of the halves to the outer ones. In H. procumbens 
L. the pollen is shed in the bud into pockets on the inner surface of 
the inner petals, which close up before the stigma developes. When 
pressed by an insect the pockets open and dust it with pollen. The 
stigma only ripens after it has grown above the level of the pollen. 
Hypericaceae (Warming: Cistiflorae) = Hypericineae (Benth. -Hooker : 
Guttiferales). Chief genus Hypericum; merged in Guttiferae (q.v.). 
Hypericum Tourn. ex Linn. Guttiferae (11). 200 sp. temp. (11 Brit., 
St John’s wort, tutsan, &c.). They are nearly all perennial herbs with 
opp., often gland-dotted leaves and cymes of firs., often forming pseudo- 
racemes or -umbels. Sta. 00 , but united into 3 or 5 groups. Develop- 
mental study shows that each of these groups arises as a simple 
papilla from the growing point, and afterwards branches; a com- 
