82 JOURNAIv 01? F'OREISTRY 



tain crosses all vegetation belts, passing gradually from the one to the 

 other; the transition from the rain-forest of Darien or from the rain- 

 forest of the Atlantic coast to the semi-dry forests of the Pacific pro- 

 ceeds step by step in steady but almost unnoticeable gradation. In 

 Darien, the real lofty rain- forest is seen only in the hinterland and on 

 the broad flats along the middle course of the Tuyra and Chucunaque 

 rivers. The foot-hills have a different character, proper of a dryer 

 climate, and which accentuates itself more and more as we approach the 

 shores of the ocean. On the other hand, descending the great collecting 

 artery of the region, the Tuyra River, we soon reach the tidal-belt and 

 are not long in noticing a brusque transition in the character of the flora, 

 the mixed forests of the interior being replaced by intensely gregarious 

 formations. Thus, on the foot-hills, a slightly increasing altitude pro- 

 duces a marked but very gradual change, while a nearer approach to 

 the low, periodically inundated coast flats is signalled by a brusque 

 transformation in the character of the forest. In the first case, the 

 passage is from the evergreen rain-forest to the semi-deciduous or mon- 

 soon-forest; in the second, we proceed by sharply defined stages toward 

 the coastal mangrove formation. 



As defined by Schimper, the monsoon-forest is characterized by "trees 

 losing their hygrophilous foliage during the dry season and renewing 

 it at or immediately before the commencement of the monsoon-rains ; 

 apart from this, they have only xerophilous organs well protected 

 against drought." This definition applies adequately to a large part 

 of the Panaman forests of the Pacific watershed with one or two dry 

 seasons. The minimum of rainfall assigned to that formation is that 

 of Panama City, 1.80 m. It is safe to assume that the amount gradu- 

 ally increases going eastward, and decreases in the opposite direction. 

 We reckon as monsoon-forests those west and south of Panama City, 

 while the dryer forests of Veraguas and Chiriqui have to be considered 

 as true xerophilous woodland. 



The typical, ever-prominent tree of the monsoon-forest of Darien 

 and the eastern Pacific coast is the Cuipo-tree, Cavanillesia platani- 

 folia, which reaches here the northernmost limit of its extension, while 

 to the southward it goes as far as Peru. It is exceptionally abundant 

 and certainly gregarious on the low hills of Darien, in the Canal Zone, 

 and appears among the remnants of the primeval forests in pastures and 

 old clearings. It is 40 to 50 m. high when fully grown, with a basal 

 diameter of over 2 m. On top of a monumental columnar trunk there 

 rests a scanty crown, so that when the tree is seen isolated it gives an 

 odd impression of disproportion, like that of a very tall and broad- 



