PRIMULA 
543 
Fir. ? or unisex., regular, i — 4-merous. Cpls. free or only 1. 
Ovules 1 in each epl., pendulous, orthotropous. Fruit one-seeded. 
No endosperm. Embryo with well developed hypocotyl. For details 
see genera. 
Chief genera : 
A. Firs, in spikes : 
1. salt water: Zostera, Phyllospadix, Posidonia, Ruppia. 
2. fresh or brackish : Potamogeton. 
B. Firs, in cymes or solitary: Cymodocea, Zannichellia. 
[Benth. -Hooker unite P. to Aponogetonaceae, Juncaginaceae and 
Naiadaceae, and place the whole order (Naiadeae) in Apocarpae. 
Warming places it in Helobieae.] 
PotentiUa Linn. (incl. Comarum Linn., Sibbaldia Linn., Tormentilla 
Linn.). Rosaceae (in. 6 b). 200 sp. chiefly N. temp, and arctic, a 
few S. temp, and Andes; 9 in Brit., incl. P. Anserina L. (silver- 
weed), P. reptans L. (cinquefoil), P. Comarum Nestl., P. Tor?nentilla 
NecK. (tormentil), &c. Herbs, usually with creeping stems which root 
at the nodes and thus multiply the plant vegetatively. There is a 
well-marked epicalyx of small green leaves outside and alt. with 
the sepals. These are the stipules of the sepals united in pairs; often 
one or more of them may be seen with two lobes or even completely 
divided. Firs, homogamous, fly- visited ; honey is secreted by a ring- 
shaped nectary within the sta. 
Poterium Linn. (incl. Sanguisoi'ba Rupp, ex Linn.). Rosaceae (in. 9). 
30 sp. N. temp. ; 2 in Brit, (burnet). P. Sanguisorba L. is anemo- 
philous with long pendulous sta. (cf. Thalictrum, Artemisia); it is 
also gynomonoecious, the ? firs, at the top of the spike opening first, 
and afterwards the £ firs, below. P. (S.) officinale A. Gray shows 
more trace of its entomophilous ancestry; the sta. are rigid and of 
a reddish colour, the stigma is less branched, and there is a nectary 
round the style (cf. Rumex and Rheum). 
Pothos Linn. Araceae (1). 30 sp. trop. As., Madagascar. Mono- 
podial (see order). Stem climbing, with adventitious roots. The 
buds break through the leaf-axils, so that the branching seems 
infra-axillary. Fir. g. P 3 + 3. 
Pourthiaea Dene. Rosaceae (11. 4). 5 sp. E. As. 
Pouzolzia Gaudich. Urticaceae (3). 35 sp. Old World trop. The 
root of P. tuberosa Wight is eaten in India. 
Prangos Lindl. Umbelliferae (6). 30 sp. Medit., Cent. As. 
Prasium Linn. Labiatae (ill). 1 sp. Medit. 
Pratia Gaudich. Campanulaceae (in). 16 sp. S. Am., Austr., trop. As. 
Premna Linn. Verbenaceae (iv). 40 sp. trop. and subtrop. (exc. Am.). 
Prenanthes Vaill. ex Linn. Compositae (xm). 27 sp. N. temp, and 
Afr. 
Priestleya DC. Leguminosae (111. 3). 15 sp. S. Afr. 
Primula Linn. Primulaceae (1). 146 sp., N. hemisph. chiefly in hilly 
