92 INTRODUCTION 
that are regarded as having been derived from ammonia, hydrogen atoms of this 
being replaced by an alcohol radical. The best known odour belonging to this 
group is that of the hawthorn (Crataegus Oxyacantha and monogyna) which 
suggests the smell of herring brine, and is due to trimethylamine. As Kerner 
mentions, the odour of hawthorn is found with slight variations in the flowers of the 
pear (Pyrus communis), medlar (Mespilus germanica), rowan (Sorbus Aucuparia), 
many meadow-sweets (e.g. Spiraea ulmifolia, chamaedryfolia), guelder-rose and way- 
faring-tree (Viburnum Opulus and Lantana), chestnut (Castanea vesca), racemose 
elder (Sambucus racemosa), wild clematis (Clematis vitalba), and barberry (Berberis 
vulgaris). Similar also is the odour of horse-chestnut (Aesculus Hippocastanum), 
manna-ash (Fraxinus Ornus), ivy (Hedera Helix), and others. I may here at once 
point out a peculiarity that is common to most of the flowers just mentioned, i.e. that 
they conceal their honey very superficially, so that it is actessible to insects with the 
shortest proboscis. In fact such insects, especially flies (Muscidae), are particularly 
conspicuous as visitors of these flowers. 
3. Benzoloid Odours. These are odours that are peculiar to the derivatives 
of benzol, in which the hydrogen atoms of a benzol nucleus are replaced by alcohol 
or acid radicals. Kerner assigns to this group the odour, due to engenol, of several 
carnations (Dianthus Caryophyllus, plumarius, superbus), also the odour of hyacinths 
(derived from cinnamyl-alcohol), the odour of Spiraea Ulmaria (derived from salicyl 
aldehyde), the cumarin-odour of woodruff, and the vanilla-odour of heliotrope; and 
beside these the respective odours of lilac (Syringa vulgaris), lily of the valley 
(Convallaria majalis), mignonette (Reseda odorata), jessamine (Jasminum officinale), 
auricula (Primula Auricula), honeysuckle (Lonicera Caprifolium), false acacia 
(Robinia Pseudacacia), violet (Viola odorata), sow-bread (Cyclamen europaeum), 
Paulownia (P. imperialis), and Ylang-ylang (Unona odoratissima), to which may 
be added the plum-like odour of Muscari racemosum and Polygala Chamaebuxus. 
The varieties of benzoloid odour just named are repeated, with some modi- 
fication, in many other flowers, a number of which are given by Kerner. The 
following possess :— 
(a) Carnation-odour : Orobanche caryophyllacea, gracilis, lucorum ; Platanthera 
bifolia, Gymnadenia conopsea, Ribes aureum, Narcissus poeticus ; 
(6) Hyacinth-odour: Silene nutans, longiflora, noctiflora; Hesperis tristis ; 
Pelargonium atrum, glauciifolium, and others ; 
(c) Woodruff-odour : Anthoxanthum odoratum, Hierochloa odorata, species of 
Melilotus (mixed in these last with the odour of honey); 
(d) Vanilla-odour: Heliotropium peruvianum and europaeum; Asperula glo- 
merata, cynanchica, longiflora; Linnaea borealis, Sambucus Ebulus, Convolvulus 
arvensis, Gymnadenia odoratissima, Nigritella nigra, Saussurea alpina, Daphne 
alpina, Epipogon aphyllum ; 
(e) Lzlac-odour : Daphne striata and pontica. 
(/) Lily-of-the- Valley-odour : Echinocactus Tetani; 
(g) Acacza-odour: Cytisus alpinus, Spartium junceum, Iris odoratissima ; 
(2) Auricula-odour: Sp. of Primula, Trollius europaeus ; 
(7) Honeysuckle-odour : Nicotiana affinis ; 
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