1858 



LIGHT 



LIGULARIA 



In the construction of greenhouses, therefore, it is 

 important they should be designed to produce the 

 maximum results during the critical light seasons. 

 Theoretical diagrams are shown in Figs. 2144-8. 



From a study of the light conditions in greenhouses, 

 it has been found that large glass is superior to small 

 glass because of the smaller amount of light-obstructing 



2148. Showing type of greenhouse constructed to obtain the maximum 

 amount of light in short winter days. Modification of type shown in Fig. 

 2147. Obstructs more light than Fig. 2147, but could be built wider. 



framework, but with present methods of construction 

 there is a limit to the size of glass that can be safely 

 employed. Moreover, high-angled roofs are much 

 superior to low roofs from the light point of view, but 

 their practical utility is somewhat limited. Experi- 

 ments with different types of glass have shown that 

 there may exist 18 per cent difference in the light-trans- 

 mitting properties of No. 1 and No. 2 quality glass, 

 and third quality glass is 33 per cent less effective 

 than No. 1 quality. A slight annual deterioration in 

 greenhouse glass must be expected owing to the for- 

 mation of a film of oil, but this can be obviated to some 

 extent. The nature of the reflecting surface of the 

 greenhouse, degree of lapping, and other factors influ- 

 ence light. In the modern large house more uniform 

 light conditions are obtained than in the early, smaller 

 houses. 



As regards the direction of the greenhouse, for most 

 purposes the east and west house is preferable for 

 obtaining light, but some crops are able to thrive better, 

 especially in the spring months, in a house running 

 north and south. Morning light being superior to 

 afternoon light, an east and west house should be 

 tilted somewhat toward the northeast, thus exposing 

 the plants more directly to the morning light and mak- 

 ing it possible to syringe with less liability to fungous 

 infection of the plants. 



Literature. 



L. Jost, "Vorlesungen uber Pflanzenphysiologie," 

 3d edition, 1913; J. Wiesner, "Der Lichtgenuss der 

 Pflanzen," 1907; G. E. Stone, "The Relation of Light 

 to Greenhouse Culture," Mass. Agr. Exp. Station Bull. 

 No. 144, 1913; E. G. Pringsheim, "Reizbewegungen der 

 Pflanzen," 1912; C. Darwin, "The Power of Movement 

 in Plants," 1880; W. Rothert, "Cohns Beitr. z. Biol. d. 

 Pflanzen," Bd. 7. 1896; A. H. Blaauw, "Extr. d. rec. 

 des travaux bot. neerl. 5, 1909;" H. Fitting, "Jahrb. s. 

 wiss. Bot. Band. 38. 41.44"; D.T. MacDougal, Memoirs 

 New York Botanical Garden, 1903. Q E STONE. 



LIGHTFOOTIA (Rev. John Lightfoot, 1735-1788, 

 author of a flora of Scotland). Campanulacese. Under- 

 shrubs or herbs (annual, biennial, perennial), of Afr. 

 and Madagascar, with very small blue, white or pink 

 fls. : Ivs. usually alternate (sometimes fascicled or oppo- 

 site), entire or toothed, small, narrow and rigid: fls. 

 variously arranged; calyx-tube adnate to ovary, the 



lobes persistent; corolla deeply 5-lobed or parted nearly 

 to base, the stamens free: fr. a caps, dehiscing at the 

 top. Species 40-50, Trop. Afr. to the Cape region. 

 Two or three species are more or less mentioned in 

 garden writings for greenhouse culture, but apparently 

 none is in the trade. L. tenella, Lodd. (L. ciliata, 

 Sond.), of the Cape, has erect woody branches and 

 bluish racemose fls. : Ivs. ovate-lanceolate, some- 

 what reflexed: 9 in. L.B.C. 11 : 1038. L. subulata, 

 L'Her. (L. sessiliflora, Sond.). Lvs. very narrow, 

 more or less spreading: st. ascending or erect, 

 somewhat woody: fls. many, blue: 12-18 in. 

 Cape. L. H. B. 



LIGULARIA (name refers to the strap-shaped 

 more or less bilabiate rays). Including Far- 

 fugium and Erythrochaste. Composite. Perennial 

 herbs, some grown in the open for the striking 

 flower-heads and leaves, but mostly indoors for 

 the large and interesting foliage, or in summer 

 bedding. 



From Senecio, to which it is often referred, 

 this genus differs largely in the character of the 

 involucre, the scales or bracts of which are in 

 one series at the insertion but of two forms so 

 that the narrow outer ones overlap the edges 

 of the broader inner ones; also in technical 

 characters of the style. Lvs. mostly long- 



petioled, broad or even orbicular or reniform, some- 

 times palmate, those on the st. smaller and bearing 

 large sheaths: heads large, reflexed or nodding, in 

 corymbs or racemes; ligules or rays mostly long and 

 narrow, usually yellow: achene glabrous, bearing soft 

 pappus. Species about 30, as now defined, from W. 

 Eu. to Siberia, Himalayas and China-Japan. The 

 plants impose no special difficulties in cult. They are 

 prop, mostly by division. 



Kaempferi, Sieb. & Zucc. (L. Farfugium, C. Koch. 

 Farfugium Kaempferi, Benth. Senecio Kaempferi, DC.). 

 Rhizomatous perennial sending up many Ivs. on slen- 

 der flocculent- woolly petioles: Ivs. large (often 6-10 

 in. across), orbicular to nearly reniform, cordate at 

 base, angular-toothed, green: fl.-sts. 1-2 ft. tall, flpc- 

 culent-woolly, branched, with only small, bract-like 

 Ivs.: heads large, with light yellow rays spreading 

 1^-2 in. across; pappus white and copious. Japan. 

 Var. a&reo-maculatus, Hort. (Farfugium grdnde, 



2149. Leopard plant, or Farfugium Ligularia Kaempferi 

 var. aureo-maculatus. ( X Yt.) 



