CLASSIFICATION OF SYMPETALAE 253 



pentacyclic and isocarpic, while the remaining five are tetra- 

 cyclic and anisocarpic ; and of the anisocarpic alliances, the first 

 three are hvpogynous and the last two epigynous. 



The three pentacyclic or isocarpic alliances are certainly 

 most nearly allied to the Archichlamydeae, for among them poly- 

 petaly still occurs, the two cycles of stamens are characteristic, 

 and occasionally the ovule has two integuments. They may be 

 regarded as lines from the Archichlamydeae in which sympetaly 

 has become prevalent. They are all hypogynous and actino- 

 morphic, and the floral formula is characteristically sepals 5, 

 petals 5, stamens 5 + 5, carpels 5. These comparatively primi- 

 tive Sympetalae are not numerous, containing only about 3,500 

 of the 42,000 species, and hence they are not the representative 

 Sympetalae. 



I. ERICALES. This includes the Clethraceae, Pirolaceae, 

 Lennoaceae, Ericaceae, Epacridaceae, and Diapensiaceae, to- 

 gether containing a little more than 1,700 species, by far the 

 largest family being Ericaceae with about 1,360 species. The 

 group is characteristically developed in high latitudes and alti- 

 tudes, and its special features are well marked. The stamens 

 are usually quite free from the petals, and this in connection 

 with occasional polypetaly gives a strong resemblance to the 

 Archichlamydeae ; while the peculiar dehiscence of the anthers 

 and their frequent appendages are very characteristic. The 

 stamens are by no means constantly in two cycles, or distinct 

 from the corolla or one another. A single cycle of functional 

 stamens may be associated with staminodia, or only a single 

 cycle may appear, or the stamen cycle may have a common ori- 

 gin with the corolla, or in some cases it may be monadelphous. 

 In short, there are transition forms to the suppression of a cycle 

 of stamens, and to a common origin of stamen cycle and corolla. 

 A multilocular ovary with numerous ovules is also a feature of 

 the alliance. 



The Epacridaceae, a well-developed Australian family of 

 heath-like plants containing nearly 300 species, are quite ex- 

 ceptional in having only one cycle of stamens and anthers with 

 longitudinal dehiscence. These exceptions seem quite funda- 

 mental, but they may be illustrations of the result of long and 

 distant separation of allied families. In any event, a com- 

 parative morphological study of Epacridaceae and Ericaceae 



