538 OX THE DESTRUCTION OF NOXIOUS INSECTS 



the celebrated professor recognised only one species to which it could 

 be compared. Unfortunately the dried specimen which he was examin- 

 ing being imperfect, his researches were necessarily limited, and 

 M. Decaisne regarded the plant as belonging to the species named by 

 Fisher and Meyer Pyrethrum elongatum, (Tanacetum elongatum, Schultz, 

 Bip.), which he with much kindness communicated to us. 



Thus the Pyrethrum of Caucasus was propagated under this name 

 to the time when M. Duchartre having made it a special object of study 

 declared (Session of Hort. Soc, Nov. 24, 1859), that this species had 

 not before been described, and that it differed by very marked charac- 

 teristics from P. elongatum. The conclusions and scientific reasons which 

 induced M. Duchartre to establish a new species for this plant are given 

 in the 5th vol. of the 'Journal de la Societie Imperiale et Centrale 

 d'Horticulture." 



Pyrethrum Willemoti is a perennial herbaceous plant, which in its culti- 

 vated state reaches to the height of about 0-50 to O60 metres. All its 

 green portions are covered with soft, cottony hair, giving it a whitish 

 appearance. It forms rounded tufts, in the middle of which shoot up 

 numerous little heads of flowers with long peduncles. The stalk is 

 erect, nearly frutescent, rounded below, striped or furrowed, a little 

 cottony towards the top. The lower leaves are large, and measure often 

 nearly eight inches in length, by a breadth of about two inches. Borne 

 by a long channelled petiole, slightly clasping at their base, they are 

 divided into seven to nine segments or pinnatifid. These segments are 

 alternate, deep, narrowed at their base, expanded at the top in unequal 

 lobes terminated by pointed teeth. In proportion as they rise on the 

 stalk, the leaves become smaller and less divided. Some of them 

 towards the tup may even be found linear and almost entire. The leaves 

 finally vary in this form during the course of vegetation. They have a 

 very bitter taste. 



The peduncles are furrowed or channelled, and have hardly any but 

 small linear leaves, and near the head (capatulum) very small green 

 scales. The little heads formed by the re-union of the flowers on a 

 common receptacle terminate each in a peduncle. The flowers of 

 the disk are yellow and those of the circumference or rays white. The 

 involucre or common calyx is composed of scales, brownish towards the 

 middle and covered with a cottony and whitish down. They are 

 imbricated, linear, the exterior ones are longer and terminate in a point, 

 the interior ones on the contrary are truncate, curved and terminating 

 in irregular teeth. The receptacle is nearly heniespherical, convex, 

 without the spangles, which are found in many other plants of the com- 

 posite family. 



The flowers of the circumference, which are also called strap-shaped 

 flowers or florets, have a corolla with a short tube and a tongue-shaped 

 limb presenting two furrows above and terminated by these rounded 

 teeth. Eadi little head is com])osed of from twelve to fifteen of these 



