DOU 



[ 305 ] 



DHA 



development of the petals which charac 

 terise double flowers. 



By these means a greater quantity ol 

 sap is supplied to the flower than the 

 natural extent of the petals can elabu 

 rate; and those parts required for the 

 extra elaboration are developed at the 

 expense of those not demanded for the 

 purpose. 



In double flowers, as was observed by 

 the late Sir J. E. Smith, the corolla is 

 much more durable than in single ones 

 of the same species, as anemones and 

 poppies, because, as he conceived, in such 

 double flowers the natural function nol 

 being performed, the vital principle o] 

 their corolla is not so soon exhausted 

 Advantage may be taken of this to pro- 

 long the duration of flowers by cutting 

 away the pistils or stamens, whichever 

 are least conspicuous, with a sharp pair 

 of pointed scissors. 



DOUCIN STOCK. See STOCK. 



DOUGLA'SIA. (In memory of the un- 

 fortunate .ZX. Douglas, botanical traveller 

 in North West America. Nat. ord., 

 Primeworls [Primulacese]. Linn., 5-Pen- 

 /arfnal-Mono<7y ma. Allied to Androsace.) 



An extremely rare, hardy, evergreen, alpine 

 plant. Seeds ; peat and loam ; should be used 

 as an alpine plant, and protected in winter; it 

 will not bear sudden changes. 

 D. niva'lis (snowy). $. Purple. Jane. Rocky 

 Mountains. 1827. 



DOYE FLOWER. Periste'ria. 



DRA'BA. (From drabe, acrid ; refer- 

 ring to one of the universal characters of 

 its Nat. ord., Critcifers [Brassicacese]. 

 Linn., 15-Tetradynamia. Connected, but 

 not in close alliance, with Aubretia, Alys- 

 sum, and Cochlearia.) 



Hardy rock or alpine plants. Yellow-flowered, 

 except where otherwise mentioned. Perennials, 

 by dividing the roots ; also with the annuals and 

 biennials, by seeds in spring, and under a hand- 

 light, in summer; peat and loam for the tender- 

 est ; sandy loam and dry situation for the hardiest. 

 They make interesting pot-plants, treated as al- 

 pines ; and that is the satest way to treat many of 

 them. 



ANNUALS. 

 D. grti'rilis (slender). . June. N. Amer. 1827. 



lu'tea (yellow). . June. South Europe. 1820. 



mura'lis (wall). J. White. June. England. 



nemora'lis (grove). $. June. Europe. 175fi. 



BIENNIALS. 

 D au'rea (golden). . June. Denmark. 1820. 



cmerea (grey). $. White. July. Siberia. 1818. 



omfu'sa (confused). 3. White. July. North 



Europe. 



Dau'rica (Daurian). $, White. July. Dauria. 



- inca'na (hoary). |. White. May. Britain. 



HERBACEOUS PERENNIALS. 

 D. Aizoi'des (Auoon-like). $. March. Wfc. 

 --^Wow(Aizuon). $. May. Carinthia. naa. 



alpi'na (alpine). i,. April. Lapland. l&iO. 

 sili'culiS'piln'sis (hairy-podded). J. AJ- 



gut. Greenland. 18:20. 



a'spera (rough). June. Siberia. 



Austrt'aca (Austrian). $. White. June. 



Austria. 1824. 



brachyste'mon (short-stamened). 4. March. 



Switzerland. 181Q. 



Brunicefu'lia (Brunia-leaved). J. June. Cau. 



oasus. 1820. 



bryoi'des (bryum-like). i. March. Tauria. 



1820. 



cilia'ris (hair-fringed-feawedj, |. March. 



Switzerland. 1/31. 



corymbo'sa (corymbed). $. White. May. 



Baffin's Bay. 1823. 



crassifu'liu (thick-leaved). -J. June. N. 



Amer. 1826. 



cuspida'ta (spine-poinWeaed). $. March. 



. Iberia. 1820. 



dasyca'nxi (hairy-fruited). White. May. Altai. 



1837. 



erieafo'lia (heath-leaved), i- June. Cau- 



casus. 1821. 



Fladnice'nsis (Fladniso). J. White. June. 



Switzerland. 1819. 



glacid'lis (icy). . June. Siberia. 1826. 



Gmdi'ni : (Gtnelin's). ^. June. Siberia. 1823. 



grand>flo'ra (large-flowered). ^. White. May. 



Altai. 183-2. 



Helne'tica (Swiss). $. August. Switzerland. 



1819- 



fti'rta (hairy). j. White. June. North 



Europe. 1823. 



inco'mpta (rough). ^. April. Caucasus. 1821. 



Lappo'nica (Lapland). J. White. April. 



Lapland. 1810. 



lasioca'rpu (woolly-iruited). J. White. May. 



Ib20. 



murice'lla (small-prickly). . White. June. 



Lapland. 1810. 



niva'lis (snowy). $. White. June. Switz- 



erland. 1824. 



obtonga'ta (oblongate). . White. May. 



Baffin's Bay. 1823. 



pilo'ia (soft-haired). *. White. June. Si- 



beria. 1825. 



re'pens (creeping). J. June. Siberia. 1818. 



rupe'titris (rock). $. June. Scotland. 



siliquo'sa (/ur^e-podded). ^. White. June. 



Caucasus. 1822. 



stella' tu (starry). ^. White. June. Pyrenees. 



1820. 



styla'ris (long-styled). 



ttunento'sa (woolly). . White. June. Switzer- 



land. 1819. 



tridenta'ta (three- toothed). 1. August. Russia. 



1838. 



DRAC^'NA. (From drakaina, a female 

 dragon ; because, if this Dragon-tree is 

 wounded, the milky juice on drying be- 

 comes a hard gum, having the same pro- 

 perties as the resinous substance called 

 Dragon's-blood. Nat. ord., Li !y worts [Lili- 

 aceae]. Linn., 6-ffexandnu \-Mnnogynia.) 



Evergreens, with white flowers, except D. nw'- 

 ans. Large pieces of the branches strike when 

 mt in strong bottom-heat ; rich, fibry loam, well 

 drained. Summer temp., 60 to- Si 1 - ;, winter, 48 

 ,0 55. 



