IRIS 
419 
Pharbitis Choisy, and Quamoclit Moench, all treated as separate 
genera in Nat . Pfif Convolvulaceae (1. 4). About 410 sp. trop. 
and warm temp. Chiefly climbing herbs or shrubs ; many are 
cultivated for their handsome flrs. ( e.g . /. purpurea Roth, the 
morning glory). /. Batatas Lam. (B. edulis Choisy) is the sweet 
potato, largely cultivated in warm countries for its tuberous roots, 
which are used like potatoes. /. (Exogonium) Purga Hayne is the 
Jalap. The rhizome gives off turnip-like roots about the size of 
apples ; they possess purgative properties on account of a resin which 
they contain. 
Iresine P. Br. Amarantaceae (4). 20 sp. Am.. Afr. 
Iriartea Ruiz et Pav. Palmae (iv. 6). 10 sp. trop. S. Am. The stem 
is supported on aerial roots (cf. Pandanus), often to a height of 8 feet 
above the soil. Some of the branches of these roots are thorny (cf. 
Acanthorhiza). In /. ventricosa Mart., the Paxiuba palm, the stem 
has a peculiar egg-like thickening about half-way up (cf. Bomba- 
caceae, Jatropha). 
Iridaceae. Monocotyledons (Liliiflorae)i 57 gen. with about 800 
sp. trop. and temp.; the chief centres of distribution are S. Afr. and 
trop. Am. Chiefly herbs with a sympodial tuber or rhizome below 
ground. Leaves usually equitant in two ranks. Infl. terminal, cymose 
(1 fir. only in Crocoideae). Fir. $ , regular or zygomorphic. Perianth 
3 + 3, petaloid, united below into a long or short tube. Sta. 3 (the 
outer whorl), with extrorse anthers, q (3), 3-loc., with axile pla- 
centae (rarely i-loc. with parietal placentae). Style usually trifid and 
frequently more or less petaloid. Ovules usually 00 , anatropous. 
Loculicidal capsule. Embryo small, in hard endosperm. 
Classification and chief genera (after Pax) : 
I. Crocoideae (flr. solitary, or several developed centrifugally 
round a central one ; plant small ; leaves not exactly in 
\ phyllotaxy) : Crocus, Romulea. 
II. Iridoideae (flrs. numerous, in spathes, several in each, 
usually regular ; stem distinct ; leaves equitant) : Iris, 
Moraea, Tigridia, Sisyrinchium. 
III. Ixioideae (similar, but spathes i-flowered; flr. often zygo- 
morphic): Ixia, Tritonia, Gladiolus, Freesia. 
[Placed in Epigynae by Benth. -Hooker; Liliiflorae by Warming.] 
Irideae (Benth. -Hooker) = Iridaceae. 
Iris Tourn. ex Linn. Iridaceae (11). About 100 sp. N. temp. 2 in Brit., 
I. Pseudacorus L., the yellow flag, and /. foetidissima L., the gladdon. 
Many sp. are cultivated. Most sp. have a sympodial rhizome with 
equitant isobilateral leaves, and small cymes of flrs. in spathes. 
Perianth petaloid, the sepals usually bending downwards at the outer 
ends ; opposite to them and almost resting on them are the petaloid 
styles, under which are the sta. with their extrorse anthers. Just 
above the anther, on the outer side of the style, is a little flap, whose 
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