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in the form of a substantial frond. Despite this burrowing 

 tendency, however, these rhizomes and stolons are not 

 roots proper, these always exist independently as rambling 

 fibres of indefinite extension, and generally bearing, in the 

 open fissures of the soil, a dense covering of root-hairs, 

 the presence of which is always a sign of health. Tree 

 ferns, as we have seen, have their trunks annually 

 strengthened by the roots sent down from the bases of the 

 new season's fronds. The trunk is formed primarily of 

 the fleshy or woody bases of the fronds. A young tree 

 fern commences with a shuttlecock crown growing on the 

 soil, each year the crop or circlet of new fronds springs up 

 inside the old one at a somewhat higher level, the old 

 fronds rot all but an inch or two at the base, which is 

 woody and permanent ; from each new frond base springs 

 a set of roots which find their way between the old stumps 

 iato the soil. In time it is obvious the crown is lifted 

 entirely free from the soil, and it is also obvious that the 

 trunk is strengthened and thickened annually, although in 

 an utterly different fashion to that of trees proper, unless, 

 indeed, we may assume a parallel in the fact that its 

 annual crop of leaves thickens its bark by a generally dis- 

 tributed ring of wood as an equivalent to an entwined ring 

 of root fibres in the fern. Anyway, this is the structural 

 process, and therein we may discover one of the main 

 conditions of the tree fern existence, viz. a climate which 

 is so constantly humid that the roots in descending the 

 trunk are never killed by drought. Such conditions 

 obtain in all tree fern districts, and to such an extent that 

 we usually find them associated with such humidity-loving 

 ferns as the delicate tribe of Filmies, which clothe their 

 trunks and form very frequently in their minuteness and 

 delicacy of structure the very antithesis of their grand 

 associates. 



In the filmy ferns we arrive so very near to the mosses, 



