506 



BOTANY 



PART II 



buted in all parts of the world. They attain their highest develop- 

 ment in the tropics. The Tree-Ferns (Cyathea, Alsophila, Dicksonia), 

 which include the largest representatives of the order, occur in 

 tropical countries, and characterise the special family of the Cyatheaceae. 

 The stem of a Tree-Fern (Fig. 470) is woody and unbranched : it bears 

 at the apex a rosette of pinnately-compound leaves or fronds, which are 



FIG. 470. Alsophila crinita. A Tree-Fern growing in Ceylon. (Reduced.) 



produced in succession from the terminal bud, and leave, when dead, 

 a large leaf scar on the trunk. The stem is attached to the soil by 

 means of numerous adventitious roots. The majority of ferns, how- 

 ever, are herbaceous, and possess a creeping rhizome, terminating 

 usually in a rosette of pinnate or deeply-divided leaves. Such a 

 habit and growth are illustrated by the common Male Fern Dryopt&ris 

 (Aspidium) filix mas, the rhizome of which is official (Fig. 471). The 



