POIVREA 



687 



POLLEN 



Stove shrub with pinnate leaves. Cuttings of half-ripe 

 shoots in sand in a close, warm case. Sandy loam and 

 leaf -mould. 

 P. galegoi'des (Galega-like). i. Pale purple. June. .St. 



Domingo. 1826. 



POI'VREA. (Named after N. Poivre, a Frenchman. 

 Nat. ord. Myrobolans [Combretaceae]. Linn. io-Decan- 

 dria, i-Monogynia. Now referred to Combretum.) 



Stove evergreen climbers. Cuttings of short, stubby 

 side-shoots, as fresh growth commences, in spring, in 

 sand, under a bell-glass, and with a little bottom-heat ; 

 sandy loam and fibrous peat, with pieces of charcoal. 

 Winter temp., 55 to 60 ; summer, 60 to 85. 

 P. Afze'lii (Afzelius's). See COMBRETUM GRANDIFLORUM. 

 barba'ta (beaided-petaled) . See COMBRETUM BAR- 



BATUM. 



cocci' nea (scarlet). See COMBRETUM COCCINEUM. 

 como'sa (tufted). See COMBRETUM COMOSUM. 

 deca'ndm (ten-stamened). See COMBRETUM DECAN- 



DRUM. 



grandiflo'r a (large-flowered). See COMBRETUM GRANDI- 

 FLORUM. 



intermedia (intermediate). See COMBRETUM COMOSUM. 

 macrophy'lla (large-leaved). See COMBRETUM LATI- 



FOLIUM. 



pilo'sa (thinly-hairy). See COMBRETUM COMOSUM. 

 POKE WEED. Phytola'cca. 



POL AN I SI A. (From polus, many, and anisos, un- 

 equal; many stamens of unequal lengths. Nat. ord. 

 Capparids [Capparidaceae]. Linn. u-Dodecandria, i- 

 Monogynia. Referred to Cleome.) 

 P. Chelido'nii (Chelidonium-like). See CLEOME CHELI- 



DONII. 



dodeca'ndra (twelve-anthered). See CLEOME BUR- 

 MAN NI. 



grave' olens (strong-smelling). See CLEOME GRAVEO- 

 LENS. 



trachyspe'rma (rough-seeded), if. Yellowish- white. 

 N. Amer. 1903. 



uniglandulo'sa (single- glanded). See CLEOME UNI- 



GLANDULOSA. 



visco'sa (clammy). See CLEOME VISCOSA. 

 icosa'ndra (twenty-anthered). See CLEOME VIS- 

 COSA ICOSANDRA. 



POLEMO'NIUM. Greek Valerian. Jacob's Ladder. 

 (From polemos, war ; according to Pliny, a dispute about 

 its discovery led to warfare. Nat. ord. Phloxworts 

 [Polemoniaceae]. Linn. 5-Pentandria, i-Monogynia.) 



Hardy herbaceous perennials. Seeds; but generally 

 division of the plant ; common garden soil. 

 P. acutiflo'rum (acute-flowered). See P. C^CRULEUM 



ACUTIFLORUM. 



borea'le (northern). Siberia. 



ccrruleum (blue). 2. Blue. June. North temperate 

 regions (Britain). 



acutiflo'rum (acute-flowered). Blue. 



a'lbum (white). 2. White. June. Britain. 



,, campanula' turn (bell-shaped). Lilac-blue, bell- 

 shaped. Northern Europe. 1892. 



disse'ctum (dissected). See P. SIBIRICUM. 



foliosi'ssimum (leafiest). See P. FOLIOSISSIMUM. 



,, grandiflo'rum (large-flowered). Brown. June. 

 India. Biennial. 



,, himalaya'num (Himalayan). Lilac-blue, much 

 larger. Himalaya. 1887. 



macula turn (spotted). 2. Striped. June. Britain. 



pili'ferum (hairy). Blue. June. N. Amer. 



,, variega'tum (variegated-leaved), i. White. June. 

 Britain. 



villo'sum (shaggy). Pale blue. August. Siberia. 

 1826. 



ca'rneum (flesh). 1-3. Salmon or flesh, changing to 

 purple. California. 1858. 



confe'rtum (crowded). \. Rich blue. North-western 

 Amer. 1885. 



melli'tum (honey-coloured). $. Pale honey- 

 white. Rocky Mountains. 1900. 



fla'vum (yellow). 1^-2. Pale yellow. New Mexico. 



foliosi'ssimum (leafiest). New Mexico, Colorado, &c. 



s,ra'cile (slender). \\. Blue. June. Dahuria. 1818. 



hu'mile (lowly). Blue. August. N. Amer. 1826. 



pulche'llum (pretty), i. Blue. June, July. 

 N. Amer. 1827. 



P. hu'mile (lowly) of Lindley. See P. HUMILE PUL- 

 CHELLUM. 



,, la' cteum (milky- flowered). See P. SIBIRICUM. 



mexica'num (Mexican), i. Blue. April. Mexico. 

 1817. 



moscha'tum (musky). See P. HUMILE. 



pauciflo'rum (few-flowered), i-ij. Yellow, tinted 

 red. Mexico. 1889. 



pulche'llum (pretty). See P. HUMILE PULCHELLUM. 



macra'nthum (large-flowered). See P. HUMILE. 



pulche'rrimum (prettiest). See P. HUMILE PUL- 

 CHELLUM. 



re'ptans (creeping). \. Lilac, blue. April. N. Amer. 

 1758. 



,, ma' jus (larger), i. Dark blue. April. 



,, Richardso'ni (Richardson's). See P. HUMILE. 



sibi'ricum (Siberian). 2. White. June. Siberia. 

 1800. 



villo'sum (shaggy). See P. C^ERULEUM VILLOSUM. 



,, visco'sum (clammy). North-western Amer. 



vulga're (common). See P. C^ERULEUM. 



POLIA'NTHES. Tuberose. (From polis, a city, and 

 anthos, a flower ; referring to its general use in city 

 decoration. Nat. ord. LUyworts [Liliaceae]. Linn. 6 

 Hexandria, i-Monogynia.) 



Greenhouse tubers. Offset tubers ; old tubers are gene- 

 rally obtained from Italy every year, and are planted in 

 rich, sandy loam ; and when growth has fairly com- 

 menced, they get the advantage of a slight hotbed to 

 forward them (but the tuber, and not the top, should be 

 kept warm), before getting them ready for rooms or 

 greenhouses. 



P. gra'cilis (slender). See P. TUBEROSA GRACILIS. 

 ,, tubero'sa (tuberous). 3. White. August. Mexico. 



1629. 



flo're-ple'no (double-flowered). 3. White. August. 

 gra'cilis (slender). 3. Pale yellow. August. 

 Brazil. 1822. 



POLIOTHY'RSIS. (From polios, hoary, and thursos, a 

 thyrse or branching inflorescence ; in allusion to the 

 colour of the inflorescence. Nat. ord. Bixacea?. Allied 

 to Idesia.) 



A hardy, deciduous tree. Seeds in a gentle heat ; 

 cuttings of half-ripe shoots in sand, under a bell-glass, 

 with gentle heat. 



P. sine'nsis (Chinese). 20-70. Yellow- white or grey. 

 Central China. 1906. 



PO'LTUM or GERMANDER. See TEUCRIUM. 



POLLEN. A complete flower is made up of four sets 

 of floral organs : (i) The sepals or calyx outside ; (2) fol- 

 lowed by the petals or corolla ; (3) by the stamens 

 bearing anthers at their apex, or consisting of anthers 

 without stalks or filaments ; and (4) by the ovary bearing 

 a stigma which may be stalked or not, and containing 

 one or more ovules or unfertilised seeds. The third set, 

 consisting of stamens, constitutes the male organs. The 

 anthers produce the powdery or dust-like granules, 

 known as pollen. When magnified the pollen grains are 

 seen to be of some definite shape, according to the species 

 of plant. The anthers are four-celled or, in some cases, 

 two-celled in their early stages, but become two or one- 

 celled at maturity by the bursting of the partition of 

 two neighbouring cells. The pollen is produced in these 

 cells by the repeated division of the tissue in the centre, 

 and the cells that immediately give rise to the pollen 

 are known as the pollen mother-cells and divide into 

 four grains mostly separate, but in heaths, whortle- 

 berries, and some others, the four remain joined in a 

 mass. In Asclepiads and orchids the pollen remains 

 united in large masses. In most natural orders the 

 grains all become separate, resembling powder to the 

 naked eye. The most common pollen grain is elliptic 

 or boat-shaped, with three furrows, and one or two of 

 these furrows may be visible, but when only one is in 

 view the pollen resembles a grain of rice. Other pollens 

 are spherical, hemispherical, oblong, triangular, or 

 variously modified. The surface may be smooth, 

 granular, spiny, finely or strongly netted, or otherwise 

 beautifully marked. It may be dry, and even winged 

 in Conifers, in the case of pollen carried by the wind, or 

 more or less viscid or clammy when intended to be 

 carried by insects or other animals. It may be colour- 

 less, or most frequently of some shade of yellow, from 



