532 
PIPTADENIA 
Piptadenia Benth. Leguminosae (i. 5). 40 sp. trop., esp, Am. P. 
rigida Benth. (Brazil) yields Angico gum used like gum-arabic. 
Piptanthus Sweet. Leguminosae (in. 2). 1 sp. Himalaya. 
Pircunia Bert. = Phytolacca Linn. 
Pirola Neck. = Pyrola Tourn. 
Pirns Hall. =Pyrus Tourn. 
Pisonia Plum, ex Linn. Nyctaginaceae (2). 40 sp., chiefly trop. The 
firs, are generally unisexual. The anthocarp is glandular and is one 
of the few fruits which are able to cling to feathers. Forbes states 
that on Keeling Island the fruits adhere to the feathers of herons in 
such quantities as sometimes absolutely to cripple them, or even to 
cause their death. 
Pistacia Linn. Anacardiaceae (ill). 5 sp. Medit., 3 E. As., 1 Mexico. 
Firs, dioecious, apetalous or naked. Fruit a drupe. P. Terebinthus 
L. yields Chian turpentine, P. Lentiscus L. the resin called mastic. 
The fruits of P. vera L. are eaten under the name Pistachio nuts. 
Pistia Linn. Araceae (vm). 1 sp. trop. Am., Afr., As., P. Stratiotes 
L., a floating water-plant, but rarely anchored by its roots to the soil, 
and therefore often blown about by wind. It is of sympodial structure, 
but the intemodes remain short and bear a rosette of large leaves ; these 
sleep at night, moving upwards from the nearly horizontal position 
which they occupy by day. The continuation shoots of the sympo- 
dium are axillary, but beside each leaf arises a stolon which grows 
out along the water and gives rise to a new plant. The infl. is small 
and monoecious ; above is a whorl of <? firs. , each with a synandrium 
of 2 sta. ; below is a ? fir. of 1 cpl. Both are naked. P. is a link 
between Lemnaceae and Araceae (q.v.). 
Pisum (Tourn.) Linn. Leguminosae (ill. 9). 6 sp. Medit. W. As. 
P. sativum L. is the common pea. The floral mechanism resembles 
that of Lathyrus, but differs much in detail (see Muller). 
Pitcairnia L’Herit. Bromeliaceae (2). 70 sp. S. Am. Most are 
terrestrial ; many form stolons at the base. 
Pithecolobium Mart. Leguminosae (1. 1). no sp. trop. Stipules 
often thorny. Fruit often coiled up like that of Medicago. P. Saman 
Benth. (trop. S. Am.) is the rain tree, so called because of a legend 
that it was always raining under its branches. The ejections of juice 
by the Cicadas are responsible for this (cf. Acer, Andira). 
Pittosporaceae. Dicotyledons (Archichl. Rosales). 10 gen. with 90 sp., 
confined (exc. Pittosporum) to Austr. Trees or shrubs, often climb- 
ing, with alt., leathery, evergreen, usually entire, exstip. leaves. Resin 
is present in large quantity in passages at the outer side of the bast. 
Firs. 2 , regular, 5-merous; sta. hypogynous; cpls. 2 or more, forming 
a i-loc. or multi-loc. ovary with parietal or axile placentation, and 
2-ranked 00 anatropous ovules ; style simple. Fruit a capsule or 
berry with albuminous seeds. Chief genera: Pittosporum, Billardiera, 
Sollya. The relationships are very obscure (see Nat . Pfl-)\ it is 
