552 



THE GARDENERS' MAGAZINE. 



July 20, 3912. 



Take the ca^e of the yellow and green 

 seeded plants already dealt with. Yellow is 

 dominant over green. On this theory, the 

 yellow seed must contain something which is 

 absent in the green. But what? It has been 

 shown that in both types there is a yellow 

 and a green pigment. The green pigment 

 at first masks the yellow colour, but as they 

 ripen and dry the green colour disappears in 

 the case of the "yellow" seeds, thus expos- 

 ing the underlying yellow pigment. In the 

 " green " forms no change takes place, and 

 consequently the underlying yellow pigment 

 remains invisible. The yellow seed must ac- 

 cordingly contain something which causes the 

 green pigment to fade. This "something" 

 is absent in the green pea. 



THE FRAGRANCE OF 



FLOWERS. 



Next to their beauty^ one of the greatest 

 charms possessed, by flowers is tJie pleasant 

 scent or fragrance they emit. We epeak 

 of the smell of the wood,s in autumn or 



spring, especially after rain, but this is 

 rather collective fragrance, due to the cha- 

 teristic odour of many trees, their bark, 

 etc. Rain, moroovor, has a great effect 

 upon vegetation, causing the dried-up her- 

 bage to bcKionie fragrant again. A meadow^ 

 especially in summer, has its own charac- 

 teristic aroma, and so, too, has a lake, a 

 wood, the sea, or high hills. In each case, 

 the scent is due to an aggregation of plant 

 scents which fill the air, and are dissemi- 

 nated by water vapour and other agencies, 

 in a sort of concentrated essence if one 

 may so term it. Jt is, to a large extent, 

 this atmoepheric perfume that constitutes 

 one of the most beneficial effects of country 

 air, for the essential oils upon which many 

 of the individual scents are based are ex- 

 tremely salubrious. Judging alone from 

 tho sturdinoss of the Scot and the health- 

 giving character of the Bournemouth dis- 

 trict (where the pine walk is especially ad- 

 vocated), we may attribute much of this to 

 the terebintliine odours in the far north 

 disseminated by the pine forests, a remark 

 which applies, equally to Norway and 

 Sweden, Canada, and other large tracts 

 where conifens grow on a big scale. Apart 

 from this regional cllVct, there is the special 

 local influence of the odour of the indivi- 

 dual flower. To speak of the numerous 

 kinds would lead one to speak of some five 

 hundred different flowers, and the matter is 

 further complicated by the fact that some 

 flowers possesfe more than one distinct type 

 of scent. 



The scent resides in epidermal cells, 

 which are situate not only in the 

 stem, and leaves, in which case the scent is 

 usually unpleasant, or in the flowers, when 

 it is usually delicious and pleasant. It 

 rarely happens, how^ever, that there is, as 

 in the common woodruff, a decided scent 

 residing in every part of the plant. Here 

 it may be that what is perceived in the stem 

 acts as a deterrent to grazing cattle, and 

 that the odour of the flower serves the main 

 object of flower fragrance — to attract in- 

 sects. The scent of the leaves and flowers is 

 usually different, as in garlic and many um- 

 belliferous plants, where the leaves are 

 malodorous, and the flower smells of boney. 

 More striking cases of the last are those 

 of the coriander, whose root smells of bugs, 

 and the hemlock, which smells like mice, 

 while in each case the flower smells like 

 honey. 



The origin of tlie scents is usually the pos- 

 session of essential oils, usually volatile^ ac- 

 companied by resin in some cases. 



As is well kno vn, some flowers smell es- 

 pecially at night, e.g., honeysuckle, night- 

 flowering stock, catchfly, evening primrose^ 

 a feature connected with the period of fly- 



root, 



ing of the moths that are long-tongued 

 enough to pollinate them. The colour .of 

 tho flowers of sucli plants is usually w^hite, 

 as in White Campion, or yellow or brown, 

 tints which are more visible in twilight or 

 dusk of summer \vhen the light is diffused 

 than blue, green, or red. But most flowers 

 emit their scent by day, some at special 

 periods, and this is again often restricted 

 to the time when the two parts of the flower 

 are mature, the scent being emitted just 

 at the time when pollination is about to 

 take place by means of the insects required 

 to bring the pollen of a different flower 

 to the stigma of the one just ready for 

 this act. And, of course, this means that 

 scents are largely given off only when the 

 flower is open. Since insects again play 

 so great va part in pollination to ensure 

 cross fertilisation, it is natural that colour 

 and scent are, to a great extent, connected, 

 and orange-coloured flowers yield much, the 

 same scent, e.g., wallflower and orange- 

 yellow^ flowered chrysanthemum. 



As a rule, white flowers give off tbe most 

 fragrance. But, contrary to the usual no- 

 tion that the rose order possesses the most 

 fragrant species, the water lily order is 

 the most fragrant order of plants. At the 

 same time roses yield a very large number 

 of different odours, which it is possible for 

 a blind persoa to distinguish. On the other 

 hand, the same kind of scent occurs in 

 widely different orders, e.g., that of lemon 

 and of oamphor. Moreover, the scent of 

 new-mown hay is common to several plants 

 of widely different orders, e.g., sw^eet- 

 scented vernal grass, woodruff, melilot, and 

 an orchid, and it is especially in evidence 

 when the plants are dry.* Amongst or- 

 chids, moreover, a great diversity of scents 

 is to be noticed, viz., honey, musk, citron, 

 allspice, cinnamon, noyau, angelica, ani- 

 seed, pomatum, violets, wallflower, fresh 

 hay, coco-nut milk. And, as remarked 

 already, flowers may possess more than one 

 odour, e.g., that of honey in the flower, 

 and the cbaracteristic valerian smell also. 

 Plants closely allied may have widely dif- 

 ferent scents, e.g., orchids (as above), 

 daphnes, limes, elders, roses, and in the 

 same genus you may find some species 

 scentless along with others that smell 

 strongly. 



The diversity of scent<5 in allied species 

 and in different orders is correlated with 

 the fact that insects are attracted to special 

 flowers (a fact probably also connected with 

 colouration). Probably! tJieir olfactory nerve 

 is specially sensitive to such, and is not like 

 the human olfactory nerve — sensitive to all 

 scents ; but often the human apparatus 

 cannot detect an odour insects can. And 

 then certain scents attract certain types of 

 insects, thus indoloid scents attract certain 

 flies and beetles, while aminoid scents at- 

 tract other beetles and hymenoptera, while 

 honey scents attract butterflies and moths. 

 Hymenoptera with paraffin scent fly to 

 paraffinoid scents in flowers. Some scents 

 are more noticeable at a distance, perhaps, 

 because the oxygen acts on them after dif- 

 fusion, e.g., lime and vine, chiefly paraf- 

 finoids. It is certain that the Humming 

 Bird Hawk Moth can detect honeysuckle 

 300 yards away, and fly straight up to a 

 plant from that distance in the dark. 



Wrapped up with this acute sense of smell 

 of insects is the existence of nauseous smells 

 coupled with warning colours in some poi- 

 sonous plants, which are poisonous to us 

 and to grazing animals, but not always to 

 insects. Doubtless a smell we can only de- 

 tect by rubbing the stem, e.g., in Fool's 

 Parsley, is noticed without by animals, as. 



too, is that of hemlock and henbane bj 

 other animals, the nightshade scent of 

 nightshade. Cattle rarely, if ever, touch 

 hemlock or nightshade, but in extreme 

 drought (of 1911) have done so with accom. 

 panying signs of madness or vertigo. 



Scents have been divided into odorous 

 and malodorous scents. Of the first we mav 

 distinguish the camphorous, citronous, myr- 

 tilloid, anisoid, rhodoid (rose), anthemisoid 

 (chamomile), v olatile oils, and others due 

 to resins, e.g., balsamoid (balm) ; others 

 e.g., nardosnioid (Tussilago or Coltsfoo{)| 

 ambrosoid, moschoid (Stork's Bill), narcis- 

 soid (Narcissus Lily), violet (violet, wall- 

 flower stock, mignonette), meliosmoid 

 (Lady's Bedstraw, lime), jasminoid (jas- 

 mine), amygdaloid (almond), cyamoid 

 (acacia), maloid (apple), tannoid. Of the 

 malodorous group, with strong disagreeable 

 smell due to volatile oils with resin, are 

 terebinthoid (conifers), peganoid (rue); 

 due to sulphurous acids, aliioid (garlic) and 

 fetid (Datura, Nicotiana, S-olonace^e), meoa- 

 nodd opium (poppies) ^ cicutoid (hemlock), 

 hircoid, goat odour (Hypericum hircinum), 

 cuminoid (coriander), ptericlosimoid (like 



fern). 



Other modes of distinguishing them are 

 according to the type of essential oil form- 

 ing the base or the hydro-carbons that sup- 

 ply them. The indoloid group, which 

 contains leucin, tyr(sin, skatol, indol, con- 

 tains aroids; and plants which have a 

 smell like rotten flesh, or excreta, aristo- 

 lochia, smelling like old tobacco, calycan- 

 thus, like fermenting wine ; and these 

 flowers have livid spots ^ red-^brown veins, 

 and green background. The aminoid group, 

 which includes those producing amine, in 

 some comibination with ammonia, include 

 hawtborn, medlar, mountain ash, dogwoodj 

 wayfaring tree^ chestnut, elder. Travellers' 

 Joy, barberry,' evening primrose, and ivy 

 which has a smel' like pickled herring. 

 Then there is the benzoloid group, includ- 

 ing scents in which benzole is replaced by 

 alcohol and acid, with the occurrence of 

 eugenol in pmks and cloves, cinnamyl 

 alcohol occurring in hyacinths, salicylic in 

 meadow siweet, corumarin in woodruff, and 

 here we may mention lilac, lily of the valley, 

 mignonette, jessamine, honeysuckle, acacia, 

 violet, etc. 



A paraffinoid scent is characteristic of 

 numbers of plants. Valerianic acid occurs 

 in valerian, pelargonic acid in rose scents, 

 oil of rue in rue oenanthic acid in vine 

 plant, lime scent in limes, nightshade scent 

 in thorn apple, mandrake, elder scent in 

 elder, hircine scent in Lizard orchis, honey 

 scent of beeswax in sloe, apricot, cherry, 

 almond, some orchids, buckthorn, rather 

 different in Bird Cherry, bedstraws, forget- 

 me-nots, phlox, wall fumitory, spurges, 

 willows, some composites, some umbelhlers, 

 e.g., angelica, cow parsnip, Burnet saxi- 

 frage, crucifers, alyssum, erysimum, tulips 



garlics, clovers. i 

 The terpenoids are derived from ethereal 

 oils without oxygen in capitate-like hairs, 

 or on special parts, as in the orange flower, 

 w^hich contains oil of neroli, gardenia, mag- 

 nolia, and the citron scent, which occurs n 

 citron, thyme, lavender scent in Lavan- 

 dula, f 

 A study of the scents of wild flowers oi 

 the countryside cannot fail to yield nianj 

 interesting facts, not only connected wit 

 the life history of insects and other animais 

 as well as the connection between soils an 

 scent— an untouched field— but there is 



world of 



* This is said to cause hay-fever, -wiliicih. may 

 due rather to the wide dissemination of myriads 

 minute poll<en grrains. 



he 

 of 



interest awaiting exploration re- 

 garding the immediate economic 

 use of the numerous oils secreted, of -vvni 

 wo have mentioned but a few. 



A. R. HOBWOOD. 



Leicester Museum. 



