INSECT POLLINATION 313 



appreciable by night than by day. The Tobacco-plant 

 has good-sized white flowers that open at night, and at 

 that time emit a strong perfume. The Evening Prim- 

 rose (GEnothera biennis) has large yellow flowers, which 

 are arranged in a conspicuous spike, and open only at 

 night; they also are fragrant, and attract moths. It is 

 probable that in many insects the sense of smell is 

 keener than in man, and they can detect perfumes at 

 distances at which we should fail to recognize them. 

 It is in their antennae that the olfactory sense is 

 situated. 



The smell of putrid meat and other decomposing 

 matter, while very offensive to man, has a peculiar 

 attraction to certain flies. There are some flowers 

 which are specially adapted for pollination by carrion 

 flies, and attract them by the kind of perfume in which 

 they delight. One such is the Wild Arum (Arum macu- 

 latum, Plate XIII.), also known as Lords and Ladies, 

 Cuckoo-Pint, and Wake Robin. The details of this 

 remarkable plant are depicted in the illustration. The 

 flowers proper are small and destitute of perianths; 

 they are arranged at the base of an axis known as a 

 " spadix." At the very base is a set of female flowers 

 consisting entirely of pistils with stigmas. Above them 

 is a group of anthers separated from the female flowers 

 by a whorl of sterile pistillate flowers; higher still is a 

 series of stamens that have been modified into radiating 

 hairs. The spadix is surmounted by a club of a dull 

 purple colour a tone resembling that of decaying 

 carrion and enclosed in a sort of protective cowl, called 

 a " spathe." We note that the club of the spadix is 

 visible at the. opening of the spathe, and that the 



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