534 



FOR TULA CA CEAE 



annual herbs, often with fleshy 1., and with stipules (sometimes repres. 

 by axillary bundles of hairs). Fls. usu. in cymes (often dich. with 

 tendency to cincinni), reg., 5 . K 2, the lower sepal (usu. ant.) over- 

 lapping the upper (the two are often regarded as bracteoles); 5; 

 A 5 + 5. or 5 PP- the petals, or some other number; G (2 8) usu. 

 (3), sup. exc. in Portulaca, i-loc. with several stigmas and 2 oo 

 campylotr. ov. on a central basal plac. The fls. secrete honey and are 

 mostly insect-pollinated. Caps, with album, seeds; that of Claytonia 

 and Montia is explosive ; embryo more or less curved round the peri- 

 sperm. C/z/^ttmz.-Calandrinia,Claytonia,Montia,Portulaca,Lewisia. 



Portulacaria Jacq. Portulacaceae. 2 S. Afr. 



Portulaceae (BH. ) = Portulacaceae. 



Posadaea Cogn. Cucurbitaceae (2). 



Posidouia Kon. Potamogetonaceae. 

 ing glass). 



Poskea Vatke. Boraginaceae (11). 



1 Colombia. 



2 Austr., Medit. (used for pack- 



Somaliland. 



Posoqueria Aubl. Rubiaceae (i. 8). 5 S. Am., W.I. 

 Posterior, the side facing to the stem on which the flower is a branch 



(upper side in most floral diagrams). 



Postea Boiss. et Blanche. Compositae (4). 4 Syria, Persia. 

 Posticous, on the posterior side. 

 Potalia Aubl. Loganiaceae. i trop. S. Am. 

 Potameia Thou. Lauraceae (il). i Maclag. 

 Potamium (Cl.), a river formation. 

 Potamobryon Liebm. Podostemaceae. 3 Mexico. 

 Potamogeton (Tourn. ) L. Potamogetonaceae. 90 cosmop. n or more 



(cf. Rubus) in Brit, (pond-weed). 



Water pi. with creeping sympodial 



rhiz. and erect leafy branches ; all 



submerged or some floating. A 



series of types occurs, beginning 



with the floating sp. and ending 



with the narrow-leafed submerged 



ones. There can be no doubt of 



the origin of the P. from land pi., 



and Schenck looks upon P. natans 



L. as the sp. least modified to suit 



a water existence, i.e. the nearest 



to the ancestral type. The upper 



1. are ovate, leathery, and float ; the 



lowersubmerged, sometimes linear. 



Then come such as P. hetero- 



phyllus Schreb. where the sub- 

 merged 1. are all narrow. Next P. 



lucens L., P. crispus L. , &c. with 



all the 1. lanceolate and sub- 

 merged. Then in P. obtnsifolins 



Mert. et Koch, P. pusilhis L.,<ic., 



the leaves are narrow and of a long 



ribbon shape. P. trichoides Cham. 



et Schlecht. represents the most 



Flowering shoot of Potamogeton 

 natans, reduced. A E. P. crispus. 

 A. Flower, enlarged. B. Single stamen, 

 showing petaloid connective, enlarged. 

 C. A fruit, enlarged. D. Embryo; 

 A, hypocotyl ; c, cotyledon, the letter 

 points to the top of the sheath which en- 

 closes the plumule. E. Floral diagram. 



A, B, D, after Le Maout and 

 Decaisne ; E, after Eichler. 



