PETASITES 
5°7 
Pentas Benth. Rubiaceae (i. 2). 10 sp. trop. and subtrop. Afr., 
Madag. 
Pentstemon Mitch. Scrophulariaceae (11. 6). 80 sp. N. Am., E. As. 
Several sp. are cultivated. The posterior sta. is represented by a 
large staminode which is bent down and lies upon the lower side of 
the corolla, out of the way of insect-visitors (cf. Scrophularia). 
Peperomia Ruiz et Pav. Piperaceae. 400 spec, trop., esp. Am. Many 
are epiphytes with creeping stems, adventitious roots and fleshy leaves 
(water-tissue under the upper epidermis, see pp. 167, 175). Firs. 
$ , with 2 sta., arranged in terminal spikes, which may, as in Piper, give 
rise to a sympodium. 
Peplis Linn. Lythraceae. 3 sp. wet places, N. temp. P. Portula L. 
occurs in Brit. It is a little annual herb, very like Moniia fontana 
with minute hexamerous firs. Self-fertilisation occurs by the bend- 
ing inwards of the sta. over the stigma. The fruit is bilocular (the 
partition does not come up to the very apex) with many seeds, but 
indehiscent. When submerged the plant has a more etiolated structure 
and becomes perennial. 
Pereskia Plum, ex Linn. Cactaceae (in). 13 sp. trop. Am., W. Ind. 
Leafy plants (see order). Some, e.g. P. aculeata Mill., climb like 
Rubus with recurved thorns. 
Perezia Lag. Compositae (xn). 70 sp. Texas to Patagonia. 
Perilla Linn. Labiatae(vi. n). 2 sp. E. Ind., China. 
Perilomia H. B. et K. Labiatae (vi. 2). 8 sp. Andes. 
Periploca Tourn. ex Linn. Asclepiadaceae (1. 1). 12 sp. As., Afr., 
S. Eur. 
Peristeria Hook. Orchidaceae (19). 5 sp. Cent. Am. Epiphytic. 
P. elata Hook, (‘el spirito santo,’ so called by the natives of Panama 
because of its resemblance to a dove) is best known. Its mechanism 
requires investigation. 
Pernettya Gaudich. Ericaceae (11. 5). 26 sp., one Tasmania and 
N. Z., the rest S. Am. and Mexico. 
Persea Plum, ex Linn. Lauraceae (1). 10 sp. trop. Am. The fruit of 
P. gratissima Gaertn. f., and other sp., is eaten under the name 
Avocada or alligator pear. 
Persicaria (Tourn.) Linn. = Polygonum Tourn. 
Personates (Benth. -Hooker). The 9th cohort of Gamopetalae (p. 135). 
Personatae (Warming). The 5th cohort of Sympetalae (p. 137). 
Persoonia Sm. Proteaceae (1). 60 sp. Austr., N. Z. 
Pescatorea Rchb. f. =Zygopetalum Hook. 
Petalostemon Michx. (ICuhnistera Lam.) Leguminosae (in. 6). 
20 sp. N. Am. 
Petasites (Tourn.) Linn. Compositae (vm). 14 sp. N. temp. P. 
officinalis Moench, the butter-bur, is common in Brit, on the banks 
of streams &c. It spreads very largely by rhizomes. It is dioecious 
(cf. Tussilago, its close ally). The male head has about 30 firs, with 
