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A TEXTBOOK OF THEORETICAL BOTANY 



The Cariceae are important only on account of Carica papaya, the 

 Papaya or Pawpaw, which is widely cultivated throughout the tropics for 

 its fruit. The plant is a small tree with a stout stem and large palmate 

 leaves. It is remarkable for the fact that it is generally unbranched, a feature 

 uncommon in Dicotyledons but frequent in Monocotyledons, e.g., Palms 

 (Fig. 1558). The tissues are permeated with a laticiferous system containing 



Fig. 1558. — Carica papaya. The Pawpaw. Fruiting tree. 

 Photograph suppHed by courtesy of the South 

 African Raihvays and Harbours Department. 



the powerful proteolytic enzyme, papain, which can attack human skin. 

 The fruit is large, varying from 6 in. to 20 in. in length, and weighs up to 

 20 lb. The skin is smooth and encloses orange-coloured flesh and numerous 

 black, parietal seeds. In fact it resembles in general appearance a melon. 

 It contains about 10 per cent, of invert sugar, sucrose being almost 

 entirely absent. 



Violaceae 



This is a small family with fifteen genera and some 800 species. Viola 

 (Fig. 1559) is the only British genus. It has been subjected to very critical 

 study, with the result that many species and varieties have been described. 

 Without going into minor differences we may mention the following 

 well-known species: V. odorata, the Sweet Violet; V. canina, the Dog 



