943 



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[PYKO 



consisting of three or four trees or shrubs 

 from tropical Africa, -with alternate oval 

 or oblong leaves, often one to two feet 

 long, and numerous small flowers in dense 

 compound racemes in the upper axils ; the 

 terminal flower female, the lower ones in 

 clusters, either all males or with a female 

 one in the centre of each cluster. Nothing 

 is known of them beyond their botanical 

 characters. 



PYCNOPTERIS. Lastrea. 



PYCXOS. In Greek compounds = close, 

 dense, compact : hence pycnocephalus, 

 close-headed, a term sometimes applied to 

 very compact kinds of inflorescence. 



PYCNOSORUS. A genus of Composites 

 of the tribe Gnaphaliece, founded on an 

 Australian cottony undershrub, with ob- 

 long-linear alternate leaves, and very small 

 but exceedingly numerous flower-heads, 

 densely clustered into a doubly compound 

 globular head of about an inch diameter. 



PYCXOSPORA. A decumbent or as- 

 cending weedy perennial, constituting a 

 genus of Leguminosce of the suborder Pa- 

 pilionaccce, having the habit foliage and 

 nearly the flowers of a Besmodium, but 

 which on account of the pod, which is not 

 jointed but ovoid and inflated like that of 

 a Crotalaria or of a Fleming ia, must be 

 classed in the tribe Flemingice. It is 

 common in South-eastern Asia, the Indian 

 Archipelago, and Northern Australia. 



PYCN03TEI/MA chinense, or Asclepias 

 paniculata, is the sole representative of 

 a genus of Asclepiadacece inhabiting the 

 mountain-slopes of Northern China. It is 

 an erect perennial herb, with opposite 

 linear leaves, terminal panicles of green 

 flowers, a five-cleft calyx, a rotate corolla 

 deeply cut into five lobes, and a simple 

 corona composed of five leaflets. The 

 fruit is unknown. [B. S.] 



PYGEUM. One of the few genera of 

 Brupaceee, consisting of trees, natives 

 of tropical Asia, with entire leaves, and 

 axillary and lateral clusters of flowers 

 more or less covered with woolly hairs. 

 The flowers are six-parted, a circumstance 

 which with the characters presented by 

 the dry fruit, with a somewhat kidney- 

 shaped stone contracted in the middle, 

 I serves to distinguish the genus from its 

 congeners. [AL T. M.] 



PYRAMIDAL. Having the figure of an 

 angular cone, but more frequently used as 

 an equivalent for Conical ; as the prickles 

 of some roses, the root of the carrot, and 

 the heads of many trees. 



PYREXA. The stone found in the inte- 

 rior of the drupe and of similar fruits, 

 caused by the hardening of the endocarp. 



PYREXACANTHA. An Indian climbing 



! shrub, with milky juice, thread-like stems, 



! and stalked elliptic entire alternate leaves, 



has been so named, and is considered to 



' constitute a genus of itself, whose position 

 I is doubtful. Lindley refers it to Artocar- 



paceoe; others to Stilaginacece. The flowers 

 are small, dioecious, arranged in spikes or 

 heads. Calyx four-parted ; stamens four ; 

 ovary detached with two pendulous ovules; 

 stigma sessile. The fruit is drupe-like, its 

 stone pitted on the outside, internally 

 spiny, the spines projecting into the seed ; 

 albumen fleshy. The name of -the genus is 

 expressive of the above-mentioned pecu- 

 liarity of the stone of the fruit. [M. T. M.] 



PYRENIUM. Either the receptacle or 

 peritheciuin of certain fun gals. 



PYRENOMYCETES. A name given by 

 Fries to the Fungi included in this volume 

 under the natural orders Sphceriacei and 

 Phacidiacei. [M. J. B.] 



| PYRETHRE. (Fr.) Anacyclus Pyre- 

 thrum. 



I PYRETHRTJM. One of the genera of 



; Compositw, very nearly allied to Chrysan- 

 themum, and with difficulty distinguished 



- from it. The distinctive features reside 

 in the presence in Pyrethrum of a pappus, 

 in the form of an elevated membranous 

 border, and in the achenes or fruits being 

 angular but not winged. The species are 

 abundant in the temperate countries of 

 the Old World ; and many of them are in 

 cultivation as ornamental greenhouse or 

 hardy plants. 



P. Parthcnium is frequently met with in 

 a wild state in this country, but it is es- 

 teemed a doubtful native, and is considered 

 to have escaped from cultivation. It is an 

 erect branching plant, a foot or more in 

 height, with somewhat downy pinnate 

 leaves; and the flower-heads less than half 

 an inch across, arranged in a terminal loose 

 corymb : the florets of the ray white, those 

 of the disk or centre yellow. The plant 

 has bitter tonic properties, like those of 

 chamomile (Anthemis nobilis) ; and is a po- 

 pular remedy in slight fevers, whence it 

 has received the name of Feverfew, in com- 

 mon with some other allied plants. The 

 smell of the whole herb is said to be par- 

 ticularly offensive to bees. The plant pro- 

 ducing the root known in shops as Radix 

 Pyrethri, or Pellitory of Spain, used as an 

 irritant and for the relief of toothache, 

 &c, is included in Anacyclus : which see. 

 The name of the present genus is derived 

 from the Greek appellation of the last- 

 named plant,— from pur ' Are,' in allusion 

 to the hot taste of the root. TM. T. M.] 



PYROLACE^. (Wintergreens.) A na- 

 tural order of corollifloral dicotyledons 

 belonging to Lindley's erical alliance of 

 hy pogynous Exogens. They are herbs with 

 simple leaves, and racemose or solitary 

 flowers; sepals five, persistent; corolla 

 regular deciduous, four to five-parted ; sta- 

 mens hypogynous, eight to ten, free and 

 perfect, the anthers opening by pores; 

 ovary four to five-celled ; style one, decli- I 

 nate. Fruit a four to five-celled capsule j 

 with central placenta? ; seeds numerous, al- ! 

 buminous; embryo minute. Natives of I 

 temperate climates in Europe, North Ame- j 

 rica, and the north of Asia. There are half j 



