DEVELOPMENT OF FLORAL ENVELOPES. 211 



occasionally the base is larger than the limb, as in the Orange flower. 

 When this attachment takes place by an articulation, the petals fall 

 off either immediately after expansion (caducous), or after fertilisation 

 (deciduous'). A corolla which is continuous with the axis and not arti- 

 culated to it, as in Campanula, Heaths, etc., may be persistent, and 

 remain in a withered or marcescent state while the fruit is ripening. 

 A gamopetalous corolla falls off in one piece ; but sometimes the base 

 of the corolla remains persistent, as in Khinanthus and Orobanche. 



Development op Floeal Envelopes. — The floral envelopes, 

 when gamosepalous and gamopetalous, flrst appear .. 



in the form of a ring, whence various cellular pro- ,mIXIiw\ 

 jections arise, representing the sepals and petals ; /> jTvfTu*^ 

 when they are polysepalous and polypetalous, the ^^'yJJJUmlly 

 ring is wanting. Even when the parts become /-V^ Vj 'fV I 

 ultimately unequal, as in Digitalis (fig. 309), they /^-^'^ /"^^\ 

 form equal cellular papillae when first developed c \_/ ,. 



(fig. 336). Kg. 336. 



Irregular flowers may be referred to regular types, from which 

 they seem to have degenerated. There appear to be three principal 

 kinds of irregularity among corollas : — 1. Irregularity by simple in- 

 equality in the development of the several segments, often along with ad- 

 hesion or atrophy, or arrest of growth : this is the most common kind. 

 2. Irregularity of deviation, when the segments, though equal, turn all 

 to the same side, as in ligulate florets. 3. Irregularity by simple meta- 

 morphosis of stamens, as in Canna. The irregular corollas of Acan- 

 thacese, Bignoniacese, Gesneracese, Lobeliacese, and Scrophulariacese, 

 are formed at first in a regular manner, by equal projections from a 

 sort of cup or ring. In Calceolaria, there is at first a scooped-out cup, 

 with four regular and very minute teeth, which are ultimately de- 

 veloped as' the corolla ; the nascent calyx has also four divisions. 

 In Begoniaceae the floral envelope at first appears as a continuous 

 ring, having five equal small segments ; some of these, especially in 

 the male flowers, disappear entirely or become atrophied. 



Inner Floral Whorls, or the Essential Orga/ns of Reproduction. 



These organs are the stamens and the pistil, the latter containing 

 the seeds or germs of young plants, and corresponding to the female, 

 while the former produces a powder necessary for fecundation, and is 

 looked upon as performing the part of the male. The presence of 

 both is required in order that perfect seed may be produced. A flower 

 may have a calyx and coroUa, and yet be imperfect if the essential 



Fig. 336. Bud of the irregular gamopetalous flower of Digitalis piUT)urea. c c, Calyx. 

 p. Corolla, which in its early development is regular, e, The stamens, at first projecting 

 beyond the corolla. 



