168 



FLORAL ENVELOPES. 



351. When all the parts of the flower axe separate, and normally 

 developed, there is no difficulty in tracing this arrangement ; but in 



many cases it is by no means an easy mat- 

 ter to do so, on account of changes pro- 

 duced by the union of one part to another, 

 by degeneration, by the abortion or non- 

 development of some portions, and by the 

 multiplication or folding of others.* Of 

 the four whorls noticed, the two outer (calyx 

 and corolla), are called floral envelopes ; the 

 two inner (stamens and pistil), are called 

 essential organs. When both calyx and 

 corolla are present, the plants are Dichlamy- 

 deous (S<j, twice, and ^at/uvs, a covering) ; 

 occasionally one or both become abortive, 

 and then the flower is either Monochlamydeous (povos, single), having 

 a calyx only, or Achlamydeous ( privative) or naked, having only 

 the essential organs, and no floral envelope. 



352. The Floral Envelopes consist of the calyx and corolla. In 

 most cases, especially in Exogens, these two whorls are easily dis- 

 tinguishable, the first being external and green, the latter internal, 

 and more or less highly coloured. If there is only one Avhorl, then, 

 whatever its colour or degree of development, it is the calyx. Some- 

 times, as in many Endogens, the calyx and corolla both display rich 

 colouring, and are apt to be confounded. In such cases, the term 

 Perianth (irigt, around, and itdo { , flower), or Perigone 1 and <-wv, 



pistil), has been applied to avoid 

 ambiguity. Thus, in the Tulip, 

 Crocus, Lily, Hyacinth, in place 

 of calyx and corolla, authors 

 speak of the parts of the peri- 

 anth, although in these plants, 

 an outer whorl (calyx), may be 

 detected, of three parts, and an 

 inner (corolla), of a similar 

 number arranged alternately. 

 Thus, the perianth of the White 

 Lily (fig. 260 p), consists of 

 three outer parts, p e, alternating 



* At the conclusion of the remarks on the organs of reproduction, notice is taken of various 

 metamorphoses produced in flowers by the causes above specified. 



Fig. 259. Flower of Scilla italiea. p' p' //, Three external leaflets, or divisions of the perianth 

 or Perigone. p" p"p", The three internal leaflets, e', Stamens, opposite to the first or external 

 leaflets, e', Stamens, opposite the second or internal leaflets, o, Ovaries united together into 

 one. *, Three styles, consolidated so as to form one. 



Fig. 260. Flower of White Lily (Lilium album), p, Perianth or Perigone, having three parts 

 exterior, p e, alternating with three interior, p i. e. Stamens, having versatile anthers attached 

 to the top of the filaments, s, Stigma at the apex of the style. 



