ANGIOSPERMS 



469 



but especially to the presence of the floral envelopes, and most of all to the 

 circumstance that the foliar structures of the flower are arranged, with rare 

 exceptions, in the form of whorls, even when the leaves of the vegetative shoots 

 arc alternate or distichous, or disposed in other similar arrangements. Each of 

 the distinct appendicular organs of the flower, viz. the perianth, androecium, and 

 gynaeceum, is usually represented by several members arranged in concentric 

 circles or a spiral ; so that one or more perianth-whorls are immediately succeeded 

 within by one or more whorls of stamens, and these by the gynseceum in the 

 centre of the flower. One or other of these whorls may however be absent, or 

 each of the separate whorls may be represented by only a single member, as 

 in Ilippuris (Fig. 330), where only one stamen and one carpel are contained within 

 a scantily developed perianth. It is only rarely that the whole flower is reduced 



ri(.. ■>,-r),—Clu>tof<ociiuiH QuiHoa.; /—/K development of the flower (in longitudinal section), /the calyx furnished 

 witli glandular hairs h, a anthers, /{•, /t carpels, s/i: ovule, x apex of the floral axis, ^horizontal section of an anther 

 with four pollen-sacs on the connective on (strongly magnified). 



to a single sexual organ, as the female flowers of Piperaceae, or the male and 

 female flowers, of some Aroideae; it is much more commonly the case that the 

 flower is composed of successive whorls of members disposed from, without inwards 

 (or from below upwards), consisting of the same or multiples of the same 

 number \ radiating from the centre on all sides like a rosette, a property which is 

 frequently partially obscured at a subsequent period by bilateral development and 

 abortion. 



77ie Floral Envelope or Perianth is only rarely entirely wanting, as in the 

 Piperace^ and many Aroideae ; more often it is simple, i. e. it consists of only 

 one whorl of two, three, four, five, or rarely a larger number of leaves (as in 

 Figs. 327, 328); in this case the perianth is frequently inconspicuous and composed 



' [To this peculiarity of structure the term 'symmetrical' is generally applied in English text- 

 books ; in the present work however this word is used in a very different sense, namely in reference 

 to any structure (foliar or floral) which can be divided into two similar halves, or the parts of which 

 are radially disposed around a central point; see p. 1S3.— Ed.] 



