86 



THE FERN BULLETIN 



"frequently fall and He procumbent though this does 

 not much affect their growth." In the mountain ra- 

 vines of Java and Malaya there occurs, also, accord- 

 ing to Christ a definite thicket formation of tree ferns 

 "over which the crowns of the forest trees form a sec- 

 ond forest." A similar "under forest" formation in 

 which screw pines (P and anus) are associated with tree 

 ferns is mentioned from Celebes. These dwarf tree 

 fern associations at high altitudes are believed to fill 

 the important role of conserving the moisture by pre- 

 venting radiation and the consequent drying out of the 

 forest floor. 



Perhaps a majority of tree ferns, however, occur 

 as an integral part of the predominant forest growth, 

 their crowns often rising nearly or quite to the level 

 of the tree tops or in not a few species exceeding it as, 

 for instance Cyathea pubeseens one of the tallest 

 Jamaican species which attains a height of 40 feet or 

 more upon the heavily forested higher ridges of the 

 Blue Mountains and easily thrusts its crown above the 

 surrounding deciduous forest. There are also certain 

 species, like Cyathea furfuracea, Alsophila parvula, 

 and Cyathea insignis which in Jamaica grows indif- 

 ferently in open or shaded situations though their oc- 

 currence in the open may have followed naturally from 

 the partial and piecemeal clearing of the land, the small 

 cleared patches remaining under cultivation for only a 

 year or two before rapidly growing up to bush. 



At least one species, Cyathea arbor ea flourishes in 

 open situations commonly in very large colonies. Jen- 

 man has described it in Jamaica as "gregarious, often 

 covering acres on fully exposed slopes everywhere 

 shunning shade," Perhaps on the latter account and 



