April, 1916. Alacran Reef — Millspaugh 423 



from the east coast of Yucatan, Cozumel Island, and the Caribbean 

 mainland; and, on that account, desired to record its vegetation at this 

 time (March, 1899). 



At the time of the charting of this reef by the British Admiralty, in 

 1842, Pajaros and Chica were "bare sand spits devoid of vegetation;" 

 Perez, the largest cay, and Allison Island, had upon them "grass* 

 and samphiret only." This record we are boimd to accept as a careful 

 and comprehensive one for the reason that on account of the dangerous 

 character of the reef it was essential that it should be accurately de- 

 scribed, even to its vegetation. Accumulated obser\'^ations from 1842 to 

 1896 added "brushwood" to the southern cays and "bushes" to Allison 

 Island, though no traces of bushes were to be found on the latter at the 

 time of our visit; this indicates one of two facts: either that they had 

 been removed, even to their roots, by fishermen for firewood, or by 

 natural erosion. The age of the stunted trees termed "brushwood," 

 as I have recorded further on under Siuiana maritima, proves that 

 "brushwood" was not on Perez in 1842 at the time of the Admiralty 

 survey. 



In searching out the vegetation of the cays a most careful survey 

 was made. Each cay was minutely examined by our party over every 

 square foot of its surface, I am certain that no species escaped our at- 

 tention. A detailed indication of each of the eighteen species fotmd is 

 given in conjunction with the map. 



The discovery, on these islets, of three species new to science, with 

 the proof that they have evolved within the known and definite period 

 of 57 years, is a fact impressive as it is important. 



Perez Island, the largest cay, rises about 5 feet in height, its 

 beach being more or less abrupt on the west and gradually sloping on the 

 east or inner coast line. It is about 2550 feet in length and about 325 

 feet wide as its broadest point. Its surface is entirely coral sand except 

 for a small cairn of weathered coral heads as indicated below. 



I was informed that a few years previous to our visit a party of men 

 was left on this cay, by the Mexican Government, w4th material for the 

 purpose of constructing a beacon. Their supplies gave out and no more 

 were sent to them. They were finally rescued by a fishing vessel and 

 brought to the mainland in a dying condition. One died before the 

 rescue and was buried at the north end of the cay. Several holes in the 

 cay attested to thejpiteous attempts of these neglected men to secure 



*Sporobolus virginicus. 

 tSesuvium portulacastrum. 



