PO NTIA PRIMUL ACE^E. 



497 



eluding only three genera, and of which there arc ten 

 species. They are aquatic plants, natives of the East 

 Indies, tropical Africa, and North and South Anio- 

 ricti ; they are ornamental, and may be easily cul- 

 tivated in an aquarium ; their properties are unknown, 

 and they have not hitherto be v en applied to any use- 

 fid purpose. The genera here united are Ponte- 

 derirt, Heteranthera, and Leptantkus. The species of 

 the two latter may be cultivated in the open air. 



PONTIA (Fabricins). An extensive genus of 

 butterflies, belonging to the family PapUiomdee, and 

 distinguished by having the lower wings formed into 

 a gutter for the reception of the abdomen ; the palpi 

 nearly cylindrical, slightly compressed, with the last 

 joints of nearly equal length, and the club of the 

 antenna- ovoid. The caterpillars are naked and des- 

 titute of the fleshy retractile appendage observed on 

 the neck of the caterpillars of the genus Papifio. 

 The genus comprises the white butterflies, so common 

 in our gardens and field*, the lame of some of the 

 species feedina: upon and occasionally entirely de- 

 stroying our cabbages, hroeoli, cauliflower, &e. They 

 are, however, subject to the attacks of various para- 

 sitic insects, especiailv the IMRcrogaster glamerafttf, 

 " Small birds'" also, observes Mr. Haworth, "destroy 

 incredible numbers of them as food, and should be 

 encouraged. I once observed a titmouse (Pai-iu 

 major) take five or six large ones to its nest in a very 

 few minutes. In enclosed gardens sea-gulls, with 

 their wings cut, are of infinite service. I had one 

 eight years which was at last killed by accident, that 

 lived entirely all the while upon the insects, slugs, 

 and worms he found in the garden. Poultry of any 

 sort will soon clear a small piece of ground, but, unless 

 they are of the web-footed kind, they do much damage 

 by scratching the earth." 



The most common species of this genus are the 

 large white butterfly (P. hnmtca;, Linn.), the small 

 white (P. rapes'), and the green veined white, P. napi. 

 Mr. Stephens, however, added several others, which 

 have been regarded by some writers as varieties only 

 of the common kinds. 



POPULUS (Linnaeus). A genus of very con- 

 spicuous forest trees, natives of Europe and North 

 America, bearing dioecious flowers, and ranging with 

 the AmcntacecB. Four species are natives of Britain, 

 viz., the abele, the hoary, the aspen, and the black 

 poplars. The Lombardy is a favourite in ornamental 

 plantations ; the black Italian produces the best tim- 

 ber; they are all propagated by cuttings of either 

 their youns; shoots or roots. 



PORTLAND-IA (Limiajus). A genus of highly 

 ornamental trees, natives of Jamaica. They belong 

 to the fifth class and first order of sexual botany, and 

 to the natural order Rnh'mcnc. This plant, to grow 

 it well, requires a strong stove heat, and is well worth 

 every care to bring it to a flowering state, as when in 

 flower it is a magnificent object. 



PORTUGAL LAUREL is the Cerasus Lmitanica 

 of Linmi'tis, a common shrubbery plant, and propa- 

 gated by seeds, which ripen in abundance upon old 



PORTULACE^E. A natural order containing 

 ten genera and fifty-five species already described. 

 The Purslane and its allies are succulent herbs or 

 shrubs with fleshy, entire, alternate leaves, and usually 

 destitute of stipules. The inflorescence is axillary 

 or terminal, solitary, or in spikes or panicles ; the 

 calvx is free or only slightlv adhering to the base of 



NAT. HIST. VOL. III. 



the germ en ; the petals are exsertcd from the calyx 

 or torn", in number five, more or less ; the stamens 

 are definite, exserted with the petals from the calyx 

 or torus ; the filaments are discrete, the anthers ver- 

 satile and two-celled ; the gertnen is superior, one to 

 three-celled, and many-seeded ; the style single, and 

 the stigmas several-elefr. The Purslane is the only 

 plant of any use, the Generality being only weeds. 



POTAMOGETON (Linnaeus). A genus of 

 aquatic perennials, all indigenous to Britain, where 

 they are known as pond-weed. The genus belongs 

 to the natural order Alismaccee. None are in cul- 

 tivation. 



POTENTILLA (Linna-us). An extensive genus 



of herbaceous perennials, found everywhere over the 



whole mountainous surface ot Europe. The flowers 



1 are rather pretty, and for the most part yellow or 



! white, and from their character are ranged in Rosacecc. 



They may be called ornamental weeds ; though there 



are a few exotic species which deserve a place in the 



flower trarden. 



PRASOPHYLLUM (Dr. Brown). A rather 

 numerous genus of tuberous-rooted herbs, natives of 

 New Holland, belonging to Orchldece. According 

 to Sweet, they should be planted out in a frame in a 

 mixture of light, loam, sand, and peat earth, and only 

 protected from frost. 



PRAWN. A small crustaceous animal belonging 

 to the long-tailed (Macrouronx), ten-legged (Deca- 

 podons) division, and to the family Palcemonidce, being, 

 in fact, the typical species of that family, and known 

 by the technical name of Pnlcemon serrntns. It is 

 highly prized as a delicate shell-fish. See PAL.*- 



MONIDJE. 



PKEMNA (Linnaeus). A genus of tropical trees 

 bearing didynamous flowers, and belonging to Vcr- 

 bcnaccce. 



PRIMUI/AOE. A much admired natural order 

 of mostly humble plants, comprising within its limits 

 seventeen genera and one hundred and forty-three 

 species. They inhabit the mountains and meadows 

 of all parts of the world, but especially in the northern 

 hemisphere. " Nothing can surpass the beauty ot 

 the little delicate Alpine Primulas, Androsaces, Are- 

 tias, and Soldanellas, with their modest blossoms 

 sometimes rivalling the whiteness of the surrounding 

 snow, and sometimes emulating the intense blue of 

 the empyrean." They are as much valued for their 

 early advent as for their intrinsic beauty ; for no sooner 

 is the snow melted, and the earth loosened by the 

 vernal airs, than these harbingers of spring put forth 

 their welcome blossoms. Besides the above named 

 genera there is the Cyclamen, the elegant Dodeca- 

 tlieon. (considered worthy of being dedicated to twelve 

 divinities), the Cortusas, Trientalis, Coris, Hatlonia, 

 Li/inncchia, Lnkima, A-nagal/ix, Micranthcmum, Cen- 

 tnnculux, Sumoltis, and Campylanthtts. The prominent 

 botanical character of the order is the fruit, one-celled, 

 with a central placenta, and the stamens opposite the 

 petal?. The properties of these plants are insig- 

 nificant, nature having thus as it were secured some 

 of her prettiest flowers from rapine, and spared us 

 kindly the pain of destroying these most delicate 

 specimens of her handiwork. The tubers of the 

 Cyclamen abound in south-eastern Europe, and are 

 eagerly devoured by swine; hence the plant is called 

 sowbread. A kind of wine is made from the flowers 

 of the cowslip, said to be useful in fevers. All the 

 genera are increased by division or seeds. 



