THE SCENT OF FLOWERS AS A MEANS OF ATTRACTING ANIMALS. 199 



by their visits, thus rendering them an important service. In the Auiicula 

 (Primula Auricula), Woodruff (Asperula odorata), Rue (Ruta graveolens), and 

 Lavender (Lavandula vera), the ilowers and foliage have the same scent, and here 

 the insects seeking for honey and pollen are allured to the flowers, whilst the 

 flowers and foliage are protected from being devoured by grazing animals by 

 one and the same substance. A uniform distribution of odorous substance over 

 different parts of the same plant is, however, comparatively rare; much oftener 

 the scent of the flowers differs from that of the foliage. Thus the Garlics (Allium 

 Chamcemoly, Sibiricum, suaveolens) develop the scent of honey in their flowers 

 which brings insects to visit them, while their leaves have a strong odour of 

 onions which keeps grazing animals at bay. In most Umbelliferee the flowers 

 have a different scent from the foliage-leaves, stem, and roots. The leaves of the 

 Umbelliferous UuryangiuTn sumbul (mentioned on p. 745, vol. i.) smell of musk, 

 the root of the Coriander (Goriandrum sativu/m) gives off an offensive odour of 

 bugs, and the Common Hemlock (Coniu/m maculatum) has a repulsive odour 

 of mice. And yet the flowers of these three Umbellifers all have a delicate scent 

 of honey, which allures insects to visit them. 



The number of scents is very great. At least five hundred can be distin- 

 guished. On attempting to classify them and to state their qualities one meets with 

 a serious difficulty, for language is not rich enough to give names to all the different 

 kinds, and nothing remains but to say that Mignonette flowers have a Mignonette 

 scent. Rue flowers have the scent of Rue, and so forth. The need of bringing this 

 multiplicity into something like order, of placing similar scents together and fixing 

 on a central point round which the others could be grouped, as has been done with 

 the ground tints and ground colours, has long been felt, but hitherto sufficient 

 attention could not be given to the need, because the chemical properties of scents 

 which must serve as the basis for any scientific division are only very imperfectly 

 known. However, in what follows the classification of scents which is attempted 

 does not pretend to completeness nor to infallibility, but is to be regarded solely 

 as a first attempt or preliminary outline to which one can turn provisionally in 

 the naming these scents. 



Five groups of floral scents may be conveniently distinguished, i.e. the indoloid, 

 aminoid, paraffinoid, benzoloid, and terpenoid scents. 



To the first group, the indoloid scents, belong those volatile substances which 

 arise from the decomposition of albuminous compounds and diffuse into the at- 

 mosphere, and in which one or several benzole nuclei are retained, as well as 

 nitrogen; examples are Leucin and Tyrosin, Skatol and Indol. The group derives 

 its name from the last-named substance. These are developed in the inflorescences 

 of numerous Aroids, in the flowers of all the South African Stapelias, in those of 

 the Balanophorese, Rafflesiacese, and Hydnorese, in the perianths of about 200 Aris- 

 tolochias, and also in those of some tropical Orchids, as, e.g. of Bolbophyllum Beccarii 

 of the Malayan flora. Sometimes the scent resembles that of decomposing mam- 

 mahan flesh, sometimes of rotten flsh (cf. vol. i. p. 196), sometimes again of decom- 



