100 



off, for if all are permitted to grow the fruit produced will be 

 small. 



Seed Selection. — Seed should be saved from the best fruits 

 only. By this is meant not so much a large fruit as one that is 

 sweet and well flavored, with a small seed cavity and few seeds ; 

 oblong fruit should be preferred to roundish ones in saving seed, 

 as they grow on plants having both stamens and pistils in the 

 same flower and these being, very largely, self-pollinated, the 

 seeds produced from such flowers are more likely to reproduce 

 their kind than the seed from roundish, melonshaped fruits, which 

 mostly grow on female plants. 



All male plants should be destroved wherever thev appear, as 

 not onlv are thev unproductive but bv their pollen being carried 

 to the fruiting plants thev tend to produce degenerate plants when 

 these are grown from the seed produced on plants growing in 

 the vicinity of the male plants. 



There is no need to fear that the other plants will not fruit if 

 the male papayas are destroyed, for the reason that there are al- 

 ways plants about having Pcrfec flowers and which provide suffi- 

 cient pollen for the fructification of the female plants. This ap- 

 plies particularly to the Hawaiian papava. 



General Remarks. — The papava is verv impatient of w^ter 

 standing around the roots and should be planted only on well- 

 drained land ; being easily injured by strong winds, it should 

 be planted in sheltered situations. Keep the land clean of wec^ls 

 and the plants well mulched. 



THE EFFECT OF THE SUN IN THE TROPICS ON 

 ANIMALS AND MAN. 



V>y TTan.s Aron, 



(Professor of Physiology in the I^niversity of IManila.") 



The rays emitted by the sun may be divided into three groups : 

 ("a) the ultra-red or heat rays; (h) the visible or lieht ravs ; (c) 

 the ultra-violet or actinic rays. Freer, P)acon. and Gibbs have in- 

 vestigated the sr)lar spectrum in Manila, and find that its range 

 on the ultra-violet side is not greater than in northern regions, 

 but its chemical activity in July as gauged by its action on oxalic 

 acid and uranyl nitrate is from five to twenty times greater than 

 in Chicago. 



ATany observers have ascribed the pecidiar effects of the trop- 

 ical sun to the action of the actinic and light rays on the human 

 body. The negative rcsidts of the exjierimenls on the American 

 troops in Manila with orange-red colored clothing as well as 

 numerous observations made in the tropics by Aron have cf)n- 

 vinced him that actinic theory cannot be maintained. 



