25 
SIGNIFICANCE OF THE FORMS. 
It will be seen at once that many of these "forms" are merely an 
expression of the different manner of the distribution of the sexes, 
hut some are distinct and have a very practical bearing upon the 
subject of breeding. Perhaps the most important are the male and 
female of the dioecious papaya, by far the most common, and to many 
the only familiar papaya; the two andromonoecious forms, correae 
and forbesii: and the two hermaphrodite forms, elongata and pen- 
tandria. There are mentioned in the above list of twelve forms and 
methods of distribution of the sexes only those w T hich have been seen 
hi Hawaii, and two other forms, forbesii, which have been so fully 
reported upon by Forbes and by Solms-Laubach, and ernstii, by 
Ernst. 
CHANGE OF SEX. 
It is a fact worthy of note that some of these forms are not con- 
stant. One may assume the r61e of another. Perhaps the most 
primary change of sex which takes place is to be observed in the 
appearance of hermaphrodite flowers on trees that have previously 
produced only staminate inflorescence. That is, form 2 may pass 
into form 3 or form 6. Not only is it known that such changes take 
place, but the conditions which may bring them about have been 
under observation. This " fruiting of the male papaya" takes place 
most freely in cool climates outside the Tropics or at high altitudes. 
In Hawaii it may be seen that these trees fruit more abundantly on 
the mountains than near the sea level. Information received by 
correspondence with experiment stations and botanic gardens in 
many parts of the world, in reply to direct inquiry, have confirmed 
this conclusion. In torrid climates the fruiting of the male is rare. 
It is to be remembered in this connection that all the staminate 
flowers of the male trees possess an undeveloped or an abortive pistil. 
The only change in the cases mentioned consists in the development 
of this pistil. 
The late M. J. Iorns ' reported the appearance of female flowers 
on male trees as a result of the removal of the terminal bud. In the 
popular literature of the papaya there are many references to the 
acquiring of fruit-bearing habits by the male tree, due supposedly 
to some injury, such as the removal of the terminal bud or the break- 
ing of the roots in transplanting old male trees. It is an interesting 
and ive fact that none of these methods of treatment bring 
about the results unfailingly, and there appear to be other conditions 
entering into the problem. Iorns undertook his experiments in part 
to disprove an idea prevalent among the native Porto Ricans to the 
» Science, n. ser.,28 (1908), No .,126. 
