THE ANGIOSPERMAE 



1 109 



familv show a reduction of stamens from five to four, and in some of these, 

 notably in Pentstemon, the missing posterior stamen is represented by a 

 partially developed rudiment, or staminode. Analogous abortion of parts 

 is commonly associated with zygomorphy in many families. Flowers in 

 which parts have been suppressed are usually called " reduced ", but the 

 question whether apparently simple flowers are always the result of reduc- 

 tion has been disputed, especially by some European botanists, w'ho have 

 maintained that certain groups of simple flowers, with only a simple peri- 

 anth or none and with only one type of sex organ developed, are in fact 

 primitive and most nearly related to the presumed gymnospermic ancestors 

 of the Angiosperms. This view has found less support in recent years, 

 though it is still upheld by some palaeobotanists. 



Evident reduction is shown by flowers in which whole categories of parts, 

 present in their nearest relatives, are missing. Thus, the common Ash, 

 Fraximis excelsior, has achlamydeous, unisexual flowers, though it belongs 

 to a family, the Oleaceae, whose flowers are normally bisexual and provided 

 with a perianth. Similarly, in the Composite genera Haastia and Xanthiiim, 

 the female flow'ers are reduced to a carpel with no perianth. Extreme reduc- 

 tion characterizes the genus Euphorbia, in which the male flower is reduced 



B 



Fig. 1082. — Male flowers of Naias. A, Half 

 open. B, Older flower with dehiscent 

 anther. {After Le Maoiit and Decaisne.) 



to a single stamen, terminal on its pedicel. In Naias, the male flower 

 consists of one stamen, with a one-membered, enveloping perianth, and the 

 female flower consists of a single, naked carpel (Fig. 1082). CaUitnche 

 has achlamydeous flowers, the place of the perianth being supplied by two 

 lateral bracteoles, between which, in the male flow'ers, stands a single 

 stamen, while the female flower has two joined carpels (Fig. 1083). Many 

 similar examples could be quoted. Some families, for example, the Araceae, 

 display a reduction series, from complete bisexual, trimerous flowers in 

 Orontium (Fig. 1084) to unisexual naked flowers with one carpel or two 

 stamens in Spathicarpa (Fig. 1085). 



Lesser degrees of reduction, involving only meiomery of certain whorls, 



