THE ANGIOSPERMAE 



"93 



one or more of which may occur in many flowers as a constant feature, not 

 merely as an occasional and abnormal character. The degree of reduction 

 varies, from staminodes which retain the size and, more or less, the form of 

 normal stamens, but are sterile, to those which are merely slight emergences 

 without any differentiation or vascular supply. The former case is illus- 

 trated by the posterior stamen in Schizant/itis, which is smaller than the 

 others. A further stage is shown by Erodiiim, where all five stamens of the 

 outer whorl are reduced to their filaments only and the final condition occurs 

 in several Scrophulariaceae and Gesneraceae, in which the posterior stamen 

 is a mere rudiment without a vascular bundle. 



The reduction or suppression of one or more stamens in a whorl may 

 be an expression of unequal development in the sectors of the floral recep- 

 tacle. If this developmental inequality is unevenly distributed, staminodes 

 may be limited either to one side of the flower, as in the latter cases cited 

 above, or to more than one sector, e.g., Valeriana, where two of the five 

 stamens are abortive and also two of the three carpels, in the same floral 

 sectors. This is a phase of zygomorphy, 

 which may or may not be accompanied by 

 zygomorphy of the corolla. 



Staminodes are not always reduced in 

 the ordinary sense of that word; they may 

 be elaborated, like the branched staminodes 

 of Parnassia, or they may be, especially in 

 Monocotyledons, transformed into petaloid 

 organs. The Zingiberaceae are good exam- 

 ples of this and the petaloid staminodes 

 may almost completely replace the sepaloid 

 corollas as attractive organs (Fig. 1167). In 

 this family only the anterior stamen, out of a 

 total of six, is fertile, the other five being 

 concrescent into one large petaloid struc- 

 ture. In Cannaceae, a closely related family, 

 the five staminodes form five separate 

 petaloid segments and even half of the single 

 fertile anther is petaloid, leaving only two 

 pollen-sacs functional. The flowers of Mes- 

 embryanthemiim have a perianth which is 

 apparently multiseriate. Actually, there are 

 no petals but only five sepals, and all the 

 coloured members are petaloid staminodes. A similar condition obtains, 

 as mentioned above (p. 1159). in Trollius, where however there is a trans- 

 ition between wholly petaloid and wholly staminoid organs which suggests 

 that there is no essential difference between the two categories of organs. 

 A unique function for staminodes is that found in Pilea (Urticaceae). Inside 

 the three perianth segments are three staminodes which are strongly bent 

 inwards with their tips below the central akene. When the latter is ripe it 



Fig. 1 167. — Flower oi Hedychiion 

 (Zingiberaceae). a, Stigma 

 projecting beyond the anther 

 ofb, the one fertile stamen, 

 c, Petaloid staminode. d, 

 the narrow petals, e, Ovary. 

 (After Velenovsky.) 



