262 Encyclopaedia of Gardening 



and clo it in a way that the most showy flowers could not excel. 

 They form a large, flattish head of the most vivid colour. The 

 Poinsettia likes a warm, moist temperature, and is hardly suitable 

 for the small " mixed " greenhouse of the amateur. It is best to 

 grow a batch in a hothouse, raising them from pieces of the old 

 stem, which should be cut up and put in sandy soil in bottom heat 

 in spring; or from side shoots taken off when old plants break into 

 growth late in spring, also in bottom heat. Loam, with sand and 

 a third each of leaf mould and decayed manure, suits. They may be 

 inserted singly in small pots, shifted when rooted to 5 -in., and from 

 those to 8 -in. The plants may be kept in a frame in summer, and 



PROPAGATING POINSETTIAS BY PIECES PROPAGATING POINSETTIAS BY PIECES 



OF OLD STEM IN SPRING. OF OLD STEM IN SPRING. 



Note a young growth starting. i. Drainage. 2. Soil. 3 Cuttings, each 



with a bud. Bottom heat should be given. 



put in a warm house in late summer to bloom. Pulcherrima is the 

 only species, but there are several varieties of it, major being one ot 

 the best. See the Botanical Magazine, t. 3493. 

 Poison Oak, Rhus toxicodendron. 



Polemonium, Jacob's Ladder, Greek Valerian (polemo-nium, from 

 polemos, war, following a dispute concerning it which led to warfare. 

 Ord. Polemoniaceae) . Useful plants for the border and rockery, of 

 which the most popular species is caeruleum, a blue perennial, 2 ft. 

 high, blooming in July. There are several varieties of it, including 

 a white and a variegated. Confertum is a nice rockery plant, with 

 blue flowers in summer, 6 ins. high. Richardsoni (syn. humile), 

 blue, i ft., is a good border or rock plant. Reptans bears satiny 

 blue bell-shaped flowers in May; height 9 ins. Sandy loam is 

 suitable. Propagation is by seeds or division in spring. 



Polianthes, Tuberose (polian-thes, from polis, a city, and anthos, 

 a flower. Ord. Amaryllideae) . See Bulbs. 



Pollen. The fertilising grains borne on the stamens of flowers. 

 In most cases the pollen is in separate grains, in Orchids it is in 

 masses. See Hybridisation. 



Pollination. The application of pollen to the stigma of a flower. 

 See Hybridisation. 



Polyanthus. See Primula. 



Polygala, Milkwort (polyg-ala, from poly, much, and gala, milk. 

 Ord. Polygaleae). Showy plants, one of the most popular of which 



