740 BOTANY PART n 



in small numbers on each inflorescence. Each consists of a coarse, fibrous 

 exocarp, which contributes to the buoyancy of the fruit in water, and thus leads to 

 the wide distribution of this palm on tropical coasts, and a hard endocarp. At the 

 base of each carpel a germinal pore is present in the endocarp (Fig. 821), but only the 

 one in relation to which the embryo lies remains permeable. The endosperm forms 

 a thick layer within the endocarp ; it is rich in fatty substances and produces the 

 COPEA of commerce. The space within the endosperm is partially filled with fluid, 

 the "milk" of the coco-nut, which is possibly of service in germination. The 

 embryo on germination develops a massive absorbent organ which' grows into the 

 cavity of the fruit and serves to absorb the reserve materials. Fig. 822 shows the 

 general habit of Coco-nut palms. 



Differences are, however, found within the order. In Areca catechu (Fig. 818) 

 the fruit developed from a similar ovary to that of Oocos is a berry, the exocarp 



becoming partly fibrous and partly succulent. 

 The white endosperm is here of stony consist- 

 ence, cellulose being stored as a reserve material ; 

 the endosperm is ruminated, i.e. the dark seed- 

 coat grows into it at many points and gives it a 

 veined appearance. The fruit of the Date Palm 

 (Phoenix dactylifera) is also a berry, but this 

 arises from one of the carpels of the apocarpous 

 gynaeceum, the other two not developing. In 

 contrast to the other genera mentioned, Phoenix 

 is dioecious. Other important economic plants 

 among the Palms are Elae'is guineensis, the African 

 Oil Palm, species of Calamus which yield Malacca 

 FIG. 821. Coco -nut after partial Cane, and species of Metroxylon, from which Sago 

 removal of the fibrous exocarp. is obtained ; the two latter are found in the 

 (Reduced. After WARMINO.) Asiatic -Australian region of the tropics. Phyt- 



elephas macrocarpa, an American Palm which 



does not form a trunk, yields vegetable ivory (the hard endosperm). Several 

 species yield a flow of sugary sap on cutting off the inflorescence, and this 

 is sometimes fermented to make Palm- wine and sometimes used as a source of 

 cane-sugar (Arenga saccharifera). 



Family 5. Araeeae. The Araceae are mostly herbs or shrubs ; 

 they take a conspicuous place as root-climbers in the damp tropical 

 forests. The leaves of some species (e.g. Monstera) have the large 

 lamina incised or perforated ; this comes about by the death of 

 definitely limited areas and is comparable to the method by which the 

 leaves of Palms become compound. The flowers are greatly reduced, 

 usually diclinous, borne on a swollen, fleshy axis ; a spathe, often of 

 bright colour and serving to render the inflorescence conspicuous, 

 is present at the base of the spike (e.g. Anthurium scherzerianum, 

 Richardia aethiopica, both of which are commonly cultivated). Fruit 

 usually a red, bluish, or white berry. 



Acorus calamus has, in the course of the last two or three centuries, spread to 

 this country from the East. It has complete, hermaphrodite flowers ; ovary tri- 

 locular. The short spadix is terminal, but is displaced to one side by the spathe 

 which resembles the foliage leaves (Fig. 823). 



