168 



DESCRIPTIVE BOTANY. 



all forms of insect life that infest dwellings. Lice upon poultry or cattle are 

 exterminated by it. Scorpions and centipedes also succumb before its potent 

 presence. 



The best powder is produced from the flower when the pollen is just mature ; 

 in fact it has been supposed that it is the pollen alone tliat is effective, but it 

 is claimed that it is the odor that effects the destruction of the insect, and 

 there seems to be reason for this belief ; if that be true, it cannot be the pollen 

 that causes the death of the insect, for the odor does not reside in the pollen 

 alone. Again, it has been asserted that the pollen possesses an independent 

 odor from the plant, which is destructive to insect life. 



The powder is produced by grinding the flowers, which have been harvested 

 just as the pollen is ripe. The powders of commerce are said to be adul- 

 terated with the pulverized flowers of anthemis. 



It is destructive to the caterpillar family, as well as the coleoptera tribe, 

 and this has been used as an argument against the odor theory. Professor 

 Riley, in 1878, showed that it destroys the cotton-worm. The reason for its 

 destructive character to insect life, while harmless to higher forms of exist- 

 ence, is not understood. Men, quadrupeds, and birds breathe it with impunity. 



TANACETTJM, L. Heads iiiaiiy-flowerecl and coryiubosely cyinose, 

 staminate flowers occupying the central part of the head. Pistillate 



flowers, wdth a tubular 3-5-toothed 

 corolla, sometimes imperfect, or partly 

 ligulate, arranged around the outer 

 edge of the head ; the little seed-ves- 

 sels, ribbed or angled, with 3-5 ridges, 

 flat on top. 



T. vulgare, L. (Tansy.) Stem erect, 

 strong, angular, leafy, and branched 

 above ; smooth and purplish, 2 to 3 feet 

 high. Leaves numerous, alternate, clasp- 

 ing, bipinnate ; segments oblong, cut, and 

 serrate ; the lower leaves bipinnate ; the 

 little leaflets trifid, spreading at the base 

 along the petiole, deep green, roughish, 

 though not hairy, deep green, paler be- 

 neath. Flowers yellow, in a terminal 

 flat corymb ; involucre hemispherical ; 

 scales imbricated, numerous, linear, lance- 

 olate, acute. Ray flowers few and inconspicuous, limb toothed. Disk flowers 

 many, perfect, tubular, .^-cleft. Stamens 5 ; anthers united ; all included 

 within the corolla tube. Ovary oblong ; style setaceous ; stigma forked. 

 Fruit small, obovate, angular, crowned with a 5-sided membranous pappus 

 containing a single seed. August. 



Geography, — The geographical range of the tansy is not very wide. Indi- 

 genous to the Crimea and adjacent parts of western Asia, it has spread 

 through middle and wCvStern Europe and northern Africa, where it is found 

 in gardens and by the roadsides near dwellings. It was brought to North 

 America by European settlers early in the colonization of New England, 

 whence it has spread throughout the Atlantic States, escaping from gardens, 

 and has become naturalized. 



Tanacetum vulgare (Tansy). 



