VALUE OF FLORAL EVIDENCE 223 



"On going farther north, into the Gulf of California, the nature of the bot- 

 tom did not change materially from what it had been along the coast from 

 Acapulco to Cape Corrientes ; it was the same viscid mud, mixed occasionally 

 with Glohigerinw and masses of vegetable matter. So we found the trawling 

 most difficult from the weight of the mud brought up, but occasionally a haul 

 was made which more than repaid us for the time spent on the less productive 

 ones. 



"In the dredgings of the Blake in the Gulf of Mexico, off the West Indies, 

 and in the Caribbean, my attention had already been called to the immense 

 amount of vegetable matter dredged up from a depth of over 1,500 fathoms 

 on the lee side of the West India Islands. But in none of the dredgings we 

 made on the Atlantic side of the Isthmus did we come upon such masses of 

 decomposed vegetable matter as we found on this expedition. There was 

 hardly a haul taken which did not supply a large quantity of water-logged 

 wood, and more or less fresh twigs, leaves, seeds, and fruits, in all possible 

 stages of decomposition."* 



In another account he refers again^ to the abundance of water-logged 

 wood, leaves, seeds, etcetera, "in all possible stages of decomposition," 

 adding that "this was especially noteworthy in the line from the main- 

 land to Cocos Island." On that portion of the cruise extending across 

 the Humboldt current from the Panama coast to the Galapagos Islands 

 Agassiz observed^ that a few fragments of leaves were obtained at a depth 

 of over 1,700 fathoms at a point nearly half way between Cape San Fran- 

 cisco and the Galapagos Islands. 



With reference to the volume of terrigenous deposits Agassiz remarks :^ 



"From the investigations made this year by the Alhatross, I am more in- 

 clined to assume that the true cause of the absence of coral reefs on the west 

 coast of Central Africa is due to the immense amount of silt which is brought 

 down the hill and mountain sides every rainy season, and which simply 

 covers the floor of the ocean to a very considerable distance from the land, 

 the land deposits being found by us even on the line from the Galapagos to 

 Acapulco at the most distant point from the shore to the side or extremities. 

 The mud in Panama Bay to the hundred-fathom line is something extraor- 

 dinary, and its influence on the growth of coral reefs is undoubtedly greatly 

 increased from the large amount of decomposed vegetable matter which is 

 mixed with the terrigenous deposits." 



Again, in his notes on the exploration of the Gulf of California, we 

 find that^ "the trawl was usually well filled with mud," and that "the 

 mud gave up the usual supply of logs, branches, twigs, and decayed vege- 

 table matter." 



* Bull. Mus. Comp. Zool., Harvard Coll., vol. xxiii, p. 12. 

 5 Op. cit, vol. xxi, 1891, p. 187. 

 « Loc. cit., p. 190. 

 'Loc. cit., p. 195. 

 8 Loc. cit., p. 197. 



