ESSENTIAL OEGANS — STAMENS. 215 



Anemone, and Tulip ; and, in these instances, the changes from 

 one to the other may be traced in the same way as in the Water-lily. 

 When there is only one whorl, the stamens are usually equal in 

 number to the sepals or petals, and are arranged opposite to the former, 

 and alternate with the latter. The flower is then isostemonous (Jsog, 

 equal, and eTri//,ui>, a stamen). When the stamens are not equal in num- 

 ber to the sepals or petals, the flower is anisostemonous (avieog, unequal). 

 When there is more than one whorl of stamens, then the parts of each 

 successive whorl alternate with those of the whorl preceding it. 

 The staminal row is more liable to multiplication of parts than the 6uter 

 whorls. A flower with a single row of stamens is aplostemonous ( aTrXo'os, 

 single). If the stamens are double the sepals or petals as regards 

 number, the flower is diplostemonous (drnXoog, double) ; if more than 

 double, polystemonous (■roXis, many). In diplostemonous and poly- 

 stemonous flowers we sometimes find that the inner stamens are the 

 younger, and thus alternate with the carpels, as in Oerastium and 

 Lilium. In this case the development is centripetal. At other times 

 the external are the younger, and the carpels alternate with the 

 older stamens, as iu Geranium and Heath. In this case the develop- 

 ment is centrifugal. The outer stamens in the latter case may repre- 

 sent interst.aminal parts analogous to interpetiolar stipules. In general, 

 when the stamens are normally developed, and are more numerous 

 than the sepals and petals, they will be found arranged in several 

 whorls, and their parts multiples of the floral envelopes. Thus, if a 

 flower has five sepals, five petals, and twenty stamens, the latter are 

 arranged in four alternate rows, having five in each. Although this 

 is the usual law, yet various changes take place by abortion, arrest- 

 ment of development, and other circrtmstances leading to abnormal 

 growth. In_this way the stamens may neither be equal to, nor a 

 multiple of, the floral envelopes, and they may even be less numerous, 

 so that the flower is miostemonous (/iiiaiti, less). In Cruciferous plants, 

 while the petals and sepals are equal in number (four), and alternate 

 in arrangement, the staniens are six in number, four long and two 

 short ; this imparity of numbers has been supposed to result from the 

 splitting of the long stamens by lateral chorisis, a presumption favoured 

 by the fact that partial union frequently exists between the two long 

 stamens placed next each other (and superposed to the antero-posterior 

 petals), that teeth are found only on the outer side of these long 

 stamens, and that in many cruciferae only four stamens exist. In the 

 case of Gloxinia, where the parts of the flower are arranged in fives, 

 there are oilly four perfect stamens, but the fifth one is seen in the 

 form of a small conical projection from the base of the corolla, and by 

 cultivation the fifth stamen is sometimes fully developed, while the 

 flowers assume a regular form, and have an erect in place of an 

 inclined position on the peduncle. 



