XXVI FIRST PRINCIPLES 



283. It is necessary, however, to be aware, that sometimes the calyx is reduced 

 to a mere rim, either in consequence of lateral compression, as in the pappus 

 {aigrette, Fr.) of many Composite, or from other unknown causes, as in some 

 Acanthaceae. 



284. If the floral envelopes are of such a nature that it is not obvious whether 

 they consist of both calyx and corolla, or of calyx only, they receive the name of 

 perianthium or perigonium. 



285. Plants have frequently no floral envelopes ; in that case, flowers are said to 

 be naked or achlamydeous. 



286. When the floral envelopes are deciduous, they fall from the peduncle, as 

 leaves from a branch, by means of an articulation ; if they are persistent, it is be- 

 cause no articulation takes place. 



287. When the margins of floral envelopes are united, the part where the union 

 has taken place is called the tube, and that where they are separate is named the 

 limb. It frequently happens that in the calyx an articulation forms between the 

 limb and the tube. 



288. Botanists generally consider that the tube of the calyx is invariably formed 

 by the union of the margins of the sepals. It is, however, probable, that it is in 

 some cases a mere dilatation and expansion of the pedicel itself, as in Esch- 

 scholtzia. 



289. When the calyx and corolla are readily distinguishable from each other, 

 they exhibit the following peculiarities : 



290. The calyx consists of two or more divisions, usually green, called sepals, 

 which are either distinct, when a calyx is said to be polysepalous, or which unite 

 by their margins in a greater or less degree, when it is called monosepalous or mono- 

 phyllous. 



291. The corolla consists of two or more divisions, called petals, usually of some 

 bright colour, different from that of the sepals, than which they are frequently 

 more developed. When the petals are distinct, a corolla is said to be polypetalous ; 

 when they are united by their margins, it is called monopetalous. 



292. If the union of the petals or sepals takes place in one or two parcels, the 

 corolla or calyx are said to be one or two lipped. These lips are always anterior 

 and posterior with respect to the axis of inflorescence, and never right and left. 



293. If the sepals or petals are of unequal size, or unite in unequal degrees, the 

 calyx or corolla is said to be irregular. 



294. When the petals are so arranged that of five the uppermost is dilated, the 

 two lateral ones contracted and parallel with each other, and the two lower also 

 contracted, parallel with each other, and coherent by their anterior margins, a flower 



s said to be papilionaceous. 



265. When a petal tapers conspicuously towards the base, it is said to be unguicu- 

 late ; its lower part is called the unguis, its upper the limb. The former is ana- 

 logous to the petiole, the latter to the lamina of a leaf. 



296. The petals always alternate with the sepals, a necessary consequence of 

 their following the laws of developement of leaves. 



297. If at any time the petals arise from before the sepals, such a circumstance is 

 due to the abortion of one whorl of petals between the sepals and those petals which 

 are actually developed. 



298. As petals always alternate with sepals, the number of each row of either 

 will always be exactly the same. All deviations from this law are either apparent 

 only, in consequence of partial cohesions, or if real, are due to partial abortions. 



299. Whatever intervenes between the bracteffi and the stamens belongs t<> the 

 floral envelopes, and is either calyx or corolla ; of which nature are many of the 

 organs vulgarly called nectaries. 



300. The dilated apex of the pedicel, from which the floral envelopes and ita- 

 mens arise, is called the torus or reccytacle. 



301. The manner in which the floral envelopes are arranged before they expand 

 is called their aestivation or pra-Jloration. 



XII. STAMENS. 



302. The whorl of organs immediately within the petals is composed of bodice 

 called stamens, which are considered the fecundating apparatus of plants. 



