1980 



A TEXTBOOK OF THEORETICAL BOTANY 



The Bromeliaceae are an interesting family of xerophytic and largely 

 epiphytic species, occurring chiefly in the forests of tropical America. The 

 axis bears a rosette of leaves without stalks but with well-developed sheaths 

 which play an essential part in the nutrition of the plant. The sheaths 

 embrace the stem and form a basin or cistern in which water and fragments 

 of rotting leaves, dead insects and the like are collected. Peltate absorption 

 hairs line the inner side of the sheath and through them dissolved sub- 

 stances and in particular nitrogenous material are absorbed. 



The leaves are markedly xerophytic in character with a strongly cuti- 

 nized epidermis and well-developed water-storage tissue. The assimilating 

 tissue is usually restricted to the upper surface. In manv the leaf margins 

 bear spines, usually small but in some species of formidable size, those of 

 Piiya chilensis (Fig. 191 1) being used by the natives as fish-hooks. There are 

 often numerous adventitious roots, which in many instances serve only for 



I 



Fig. 191 1. — Piiya chilensis. Plant with inflorescence 

 about seven feet hi<ih. Cambridge Botanic 

 Garden. 



fixation, secreting an adhesive material to assist in anchoring the plant on 

 its support. 



The flowers are hermaphrodite and trimerous, with an outer sepaloid 

 and inner petaloid perianth, stamens six in number often epipetalous, with 



