1722 A TEXTBOOK OF THEORETICAL BOTANY 



) 



Fig. 1597- — Floral dia- 

 gram of Beta. Cheno- 

 podiaceae. 



The androecium consists usually of the same number of stamens as 

 there are calyx lobes, the stamens being inserted opposite the lobes. The 

 filaments are free and the anthers two-celled. Staminodes are rare. 



The gynoecium is syncarpous, composed of two or sometimes three 

 carpels. The ovary is superior, unilocular, possessing a single basal, 

 campylotropous ovule. 



The fruit is a nut or akene enclosed in a persistent perianth. It is usually 

 indehiscent or occasionally circumscissile. 



The seed is usually endospermic, the embryo being curved or even 

 spirally twisted in the endosperm. 



The family is one of moderate size containing about seventy-five genera 

 and 500 species showing an interesting geographical distribution. There are 

 nine chief districts where the bulk of the genera occur, namely: 



1. Australia. Low-lying salt plains. 



2. The Pampas of South America. 



3. The Prairies of North America. 



4. The Mediterranean coast. 



5. The Karroo in South Africa. 



6. The Red Sea shore. 



7. The south-west Caspian coast. 



8. Central Asian deserts. 



9. The salt steppes of eastern Asia. 



The anatomical features of this family are important. Anomalous stem 

 structure is general, and is due to the appearance of pericyclic rings or 

 strips of cambium, which originate and lose their activity successively, 

 forming secondary bundles and conjunctive tissue. Two extreme types are 

 known: the one results in concentric zones of xylem and phloem, the other 

 results in vascular bundles embedded in prosenchymatous conjunctive 

 tissue and arranged in various ways either regularly or irregularly. 



According to Volkens the family may be divided into two sub-famiHes 

 based on the way in which the embryo is arranged in the seed. These are 

 the Cycloloboideae and the Spiroloboideae. 



