1 86 TREE FERNS. 



quently they rose up to a height of forty feet, without a 

 single branch, standing as it were, like the columns of a 

 thousand years, in the Piazzas of the Eternal City." * 



So also the late Mr. Joseph Thomson, describing the 

 forest growing on the foot hills of the Unambara moun- 

 tains, in Eastern Africa, opposite Zanzibar, says: 



" It was indeed a marvellous forest every tree a vegetable 

 giant, rising 70 or 100 feet before branching, and then form- 

 ing a parachute-shaped crown, through which the rays of the 

 sun in vain attempted to penetrate. Little less gigantic than 

 the trees were the creepers none of your slender convolvuli 

 or ivies, but massive fellows, as thick as a man's thigh, hang- 

 ing aloft from tree to tree, or twisting up their stems. 

 Everything was strange, grand, and colossal." f Many of the 

 trees," (he goes on to say) "had crowns of leaves three feet 

 long by one foot in breadth," 



and the consequent twilight beneath their shade was 

 so deep, that he informs us : " We actually had to wait 

 an hour, after the sun rose, before we had sufficient 

 light to enable us to proceed."** 



This dense canopy of foliage, it is desirable to bear 

 in mind, consists not merely of the leaves of these great 

 trees themselves, but also of those of the innumerable 

 lianas which spread themselves, like matted cordage, 

 all over their tops, just as water plants rise up from 

 the bottom, and spread themselves over the surface 

 of a pond, exposed to the air and sunshine. More- 

 over, all this mass of verdure, by excluding the air 

 and sunlight, acts as a condenser to the vapours, 

 continually rising from a soil saturated by the tre- 



* The Heart of Africa, by Dr. Schweinfurth, 2nd edit., 1874, Vol. 

 i, p. 528. 



f To the Central African Lakes and Sack, by Joseph Thomson, 

 Vol. i, p. 52. Ibid., p. 56. ** Ibid., p. 55. 



