DIFFERENT KINDS OF CASTILLA. 23 



may not be utilized. The fruits are produced in large quantities and, 

 if the seeds were not in demand, would be of no value to the planter. 

 The aggregate amount of milk they contain must be considerable, 

 since on the slightest injury a large drop of creamy liquid exudes. 

 This continues to be the case as long as the fruit remains green, but 

 as soon as it turns yellow the milky juice disappears except from the 

 seed itself. Presumably it is changed, as in figs and in the fruits of 

 the family Sapotacea?, into the juices which render the pulp attractive. 

 The birds are apparently fond of the ripe fruits of Castilla. To diy 

 the fruits gradually would probably mean the destruction of the rub- 

 ber in the same way as in normal ripening, so that it might be neces- 

 sary to cut or crush the fruit clusters to induce prompt drying, or 

 to extract the milk and other juices by pressure, followed by washing 

 and the separation of the rubber. 



In case it should be found that rubber could be obtained from the 

 unripe fruits, it would probably not be necessary to pick them by 

 hand. They are so attached along the simple branches (PL XVIII, 

 fig. 2) that several of them could be brought down by a single motion 

 of a forked stick. 



Prussic acid in Castilla seeds. — In examining the fresh seeds of Cas- 

 tilla a distinct odor of prussic acid was noticed, a fact which may have 

 bearing upon the physiology of rubber, since the same substance occurs 

 in the seeds of Sapotacese, the family which furnishes gutta-percha, 

 and is also known to exist in the rubber-yielding genus Manihot, of 

 the famity Euphorbiacea?, to which the Para rubber tree, Hevea, also 

 belongs. 



SPECIES AND VARIETIES OF CASTILLA. 



hooker's monograph op castilla. 



Sir Joseph Hooker wrote what might be termed a monograph of 

 Castilla in 1885, a in which four species or varieties were described, 

 though no new botanical names were assigned to them. The charac- 

 ters of the fruits were chiefly relied upon, and these are described as 

 follows: 



I. Castilloa elaslica. Fruiting receptacle (in Honduras specimens) 1\ to 2 inches 

 in diameter; ripe carpels coriaceously fleshy, with pyramidal free pubescent crowns 

 one-third inch high; crown 3 to 4 grooved laterally, with rounded angles and obtuse 

 depressed 4-lobed tips. Seeds one-fourth to one-third inch in diameter; more or 

 less immersed in the free crown of the carpel; testa white, papery when dry; coty- 

 ledons thick, plano-convex; radicle minute, superior. 



The character by which I identify this with the plant of Cervantes is that of the 

 free part of the ripe carpels, which that author describes as " apice excavato;" in all 

 the other forms noticed below these crowns are acutely 3 to 4 angled, with acute tips. 



« On the Castilloa elastica of Cervantes, and some allied rubber-yielding plants. 

 Trans. Linn. Soc, London, 2d ser., 2:209. 



