THE ANGIOSPERMAE 



"45 



B 



Fig. 1 121. — Scabiosa columbaria. A, General involucre 

 around inflorescence. B, Special involucre around 

 a single flower. {After Le Maout and Decaisne.) 



achlamvdeous there are such diverse and unrelated types as Piperaceae, 

 Ceratophyllaceae, SaHcaceae, Myricaceae, CalHtrichaceae, Typhaceae and 

 Lemnaceae. 



Many other famihes are partly achlamydeous. In the Betulaceae the 

 female flowers, and in the Cor^laceae the male flowers, have no perianth, 

 although the flowers of opposite sex have one which is small and simple. 

 A few families contain one or more genera which are exceptional in being 

 achlamydeous. Examples of these are Naiadaceae {Zostera), Euphorbiaceae 

 {Euphorbia) and Potamogetonaceae (Riippia). A small number of genera 

 may even contain certain achlamydeous species, e.g., Fraxinus excelsior 

 (Fig. 1 122), although the rest of the species in that genus possess more or 

 less complete perianths. 



Fig 1 1 22. — A, Fraxinus ormis, hermaphrodite flower with perianth. B. F. 

 excelsior, achlamydeous male flower. C, The same, female flower with 

 two staminodes. (After Engler-Prantl.) 



