156 STERILITY. CuAP. XVIII. 



for flowers to become double, and this tendency is inherited. 

 Moreover, it is notorious that with hybrids the male organs 

 become sterile before the female organs, and with double 

 flowers the stamens first become foliaceous. This latter fact 

 is well shown by the male flowers of dioecious plants, which, 

 according to Gallesio,^^^ first become double. Again, Gart- 

 ner ^^° often insists that the flowers of even utterly sterile 

 hybrids, which do not produce any seed, generally yield 

 perfect capsules or fruit,- a fact which has likewise been 

 repeatedly observed by Naudin with the Cucurbitace<e ; so 

 that the production of fruit by plants rendered sterile through 

 iny cause is intelligible. Kolreuter has also expressed his 

 unbounded astonishment at the size and development of the 

 tubers in certain hybrids; and all experimentalists^^^ have 

 remarked on the strong tendency in hybrids to increase by 

 roots, runners, and suckers. Seeing that hybrid plants, 

 which from their nature are more or less sterile, thus tend to 

 produce double flowers ; that the}^ have the parts including 

 the seed, that is the fruit, perfectly developed, even when 

 containing no seed ; that they sometimes yield gigantic 

 roots ; that they almost invariably tend to increase largely by 

 suckers and other such means ; — seeing this, and knowing, 

 from the many facts given in the earlier parts of this chapter, 

 that almost all organic beings when exposed to unnatural 

 conditions tend to become more or less sterile, it seems much 

 the most probable view that with cultivated plants sterility 

 is the exciting cause, and double flowers, rich seedless fruit, 

 and in some cases largely-developed organs of vegetation, &c., 

 are the indirect results — these results having been in most 

 cases largely increased through continued selection by man. 



*^' 'Teoria della Riproduzione ^^^ ' Bastarderzeugung,' s. 573. 



V eg.,' 1816, p. 73. »" Ibid., s. 527. 



f 



