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Show :VIOLA TRICOLOR. 124 CHAP. IV. . t oTowino· close by, produced uncovered plan t of tho same vane, y' hoi ch proo duce capsu l cs wl l en 105 fine capsules. The few flowerf~ ~t'lised by the curling inwurcls d d e perhaps er I . insects are exclu o 'ar . er for by this mo::tns poll.on-grams of the petals as t~ey ':~~ht' be inserted into tho. ca~Ity _of tho adhering to the papillre g bl th t their fertilis::ttion IS effected, stigma. But it is more pro~a T~ri;s and cert::tin minute beetles as Mr. Bonnett suggests, yd h'ch cannot be excluded by any which haunt the flowers, an ~ / ·tilisers. but I have n1oro than net. Humble-bees are the usua) ert work ~ith tho under sides of once seen fli.e s (Rl~ t· n ia rostrata a ' d h . Y d ted with pollen; an avmg their bodies, heads and legs ':s.t d I found them ::tftor a few fl which they viSI e , f marked the owers . . f h w lono· a time tho flowers o days ferti'1iS' e d ·* It IS CUriOUtSh or ]a0n ts maby be watched wi. t h ou t the heartsoa~e and of ~0I?~t ~he%.p During the summer of 1841, I an insect being s~en to ;I:{ for more than a fortnight , ·ome ~argo observed many times a ~ . . ·arden before I saw a '·mgle clumps of heartsease gro~mg In t~~r ~umm~r I did the same, but humble-bee at work. Dunn~ ~n~umble-beeF; visiting on thi' e sueat last saw some dark-col,ou~~wer in several clumps; and almost cessive days almost .every withered and produced fine capsules. ~11 these flowers quiCk~y te of the atmosphere is necessary I presume th~ t a certain sta that as soon as this occurs the for the secretiOn of nectar, athnd d emitted and in1mecliately insects discover the fact by e o our ' frequent the flowers. . the . d f insects for their complete As the flowers requue ai o * I should adu that this fly apparently did not suck the nectar, but was attracted by t~e papillro which surround the shgma. H. Muller abo saw a small bee, an Andrena, which could ~ot re~ch the neetar, repeatedly ms~rtmg its proboscis be_neath the. st1gma~ where the pap1llro are s1tuate~, so that these papillro must be m some way attractive to insects. A writer asserts (' Zoologist,' vol. iii.-iv. p. 1.225) that . ~ moth ( Plusia) frequently v1s~ts the flowers of the pansy. H1ve-bees do not ordinarily visit them, but a case has been recorded (' Gardeners' Chronicle,' 1844, p. 374) of these bees doing so. H. Muller has also seen the hi vc-boe at woi}~' b. t ouly on the wild sma. - u · bst flowered form. He givf.s ~ the ('Nature,' 1873, P· 45) 0 ~ . . m. scc ts wh'tch he has seenf iv isitm. gd b th the large and small- owere foor ms From hI' S accou nt ' I su.s - t th t the flowers of phmts m ;es~ate ~f nature arc visited mhore frequently b Y m. sec ts· t. hn'. n , t Hose of the cultivated vnl'IO~les. uck~ has seen ·cvcral buttm:fhos ~ ts in()' the flower::; of wild pan. ' and this I haY never observtedl mel ~nrdens, thoug.h I have wa cle .< ·ears. tho flowers dunng many ) CHAP. IV. VIOLA TlUCOLOR. 125 fertilisation, and as they are not visited by insects nearly so often as most other nectar-secreting flowers, we can understand the remarkable fact discovered by H. Muller and described by him in' Nature,' namely, that this species exists under two forms. One of these bears conspicuous flowers, which, as we have seen, require the aid of insects, and arc adapted to he cross-fertilised by them ; whilst tho other form has much smaller and less conspicuously coloured flowers, which arc constructed on a slightly different plan, favouTing self-fertilisation, and arc thus adapted to ensure the propagation -of the species. The selffertile form, however, is occasionally vi itod, and may be crossed by insects, though this is rather doubtful. . In my first experiments on Viola tricolor I was unsuccessful in raising seedlings, and obtained only one full-grown cro. ·sod and self-fertilised plant. Tho former was 12~ inches and the latter 8 inches in height. On the following year several :flowers on a fresh plant were eros od with pollen from another plant, which was known to be a distinct seedling; and to this point it is important to attend. Several other flowers on tho same plant were fertilised with their own pollen. The average number of seeds in the ten eros eel capsules was 18 · 7, and in the twelve · self-fertilised capsules 12 · 83; or as 100 to 69. These seeds, after germinating on bare sand, were planted in pail's on the opposite sides of five pots. They were first measured when about a third of their full size, and the crossed plants then averaged 3 · 87 inches, and tho self-fertilised only 2·00 inches in height; or as 100 to 52. They wore kept in the greenhouse, and did not grow vigorously. Whilst in :flower they were again measured to the summits of their stems (see Table XLI.), with the following result:-- The average height of the fourteen crossed plants is here 5 ·58 inches, and that of tho fourteen self-fertilised 2 · 37; or as 100 to 42. In four out of the fi vc pots, a crossed plant :B.owel'ed before any one of tho self-fertilised; as likewi e occurred with the pair raised during the previous year. These plants without being disturbed were now turned out of their pots and planted in the open ground, so as to fol'm five separate clumps. Early in the following sumn1er (1869) they flowered profusely, and being visited by bumble-boos ot many capsules, which were carefully collected from all tho plants on both sides. The crossed plants produced 167 capsules, and the self-fel'tilised only 17; or as 100 to 10. So that the crossed plants wel'e more than twice the |