1788 



A TEXTBOOK OF THEORETICAL BOTANY 



with alternate, stipulate leaves. Stellate hairs are very common in the 

 younger parts and mucilage-containing cavities are often formed in the 

 cortex. 



The arrangement of the families within the order varies somewhat 

 among different authors. Engler, Rendle and Wettstein include the follow- 

 ing common families: Tiliaceae, Bombacaceae, Sterculiaceae and Malvaceae. 

 Hutchinson separated the first three into an independent order which he 

 calls the Tiliales, and retains Malvaceae with certain small families in the 

 Malvales. We shall consider the Malvaceae in detail but may first mention 

 certain important points about the other three families. 



Rendle considers that the Malvales show a relationship with the Gutti- 

 ferae in their regular, hypogynous, pentamerous flowers and also in the 

 structure of the androecium. On the other hand he thinks they may be 

 related to the Euphorbiales in the structure of the ovary and in the endo- 

 trophic course of the pollen tubes. 



The Tiliaceae are an important family with thirty-five genera and about 

 380 species, occurring mainly in tropical and temperate regions of south- 

 eastern Asia and Brazil. They are mostly trees or shrubs with alternate, 

 stipulate leaves. The inflorescence (Fig. 1680) is cymose though in such 



Fig. 1680. — Till 



ildti 



1' low fnii^ ^huot. 



genera as Tilia it may be complexly modified. The family is distinguished 

 from the Malvaceae, first because the stamens are either free or only 

 united at the base and secondly because the anthers have only two pollen 

 sacs instead of four as in the Malvaceae. 



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