152 STERILITY FKOM THE DEVELOPMENT Chap. XVIIL 



the antagonistic state, commonly arises from a plethoric condition. 

 On the other hand, extremely poor soil sometimes, though rarely, 

 appears to cause doubleness : I formerly described 101 some completely 

 double, bud-like, flowers produced in large numbers by stunted 

 wild plants of Gentiana amarella growing on a poor chalky bank. I 

 have also noticed a distinct tendency to doubleness in the flowers of 

 a Eanunculus, Horse-chestnut, and Bladder-nut (Ranunculus repens, 

 sEsculus pavia, and StaphyJed), growing under Tery unfavourable 

 conditions. Professor Lehmann l0 ' 2 found several wild plants growing 

 near a hot spring with double flowers. With respect to the cause of 

 doubleness, which arises, as we see, under widely different circum- 

 stances, I shall presently attempt to show that the most probable 

 view is that unnatural conditions first give a tendency to sterility, 

 and that then, on the principle of compensation, as the reproductive 

 organs do not perform their proper functions, they either become 

 developed into petals, or additional petals are formed. This 

 view has lately been supported by Mr. Laxton, 103 who advances the 

 ease of some common peas, which, after long-continued heavy rain, 

 flowered a second time, and produced double flowers. 



Seedless Fruit. — Many of our most valuable fruits, although con- 

 sisting in a homological sense of widely different organs, are either 

 quite sterile, or produce extremely few seeds. This is notoriously 

 the case with our best pears, grapes, and figs, with the pine-apple, 

 banana, bread-fruit, pomegranate, azarole, date-palms, and some 

 members of the orange-tribe. Poorer varieties of these same fruits 

 either habitually or occasionally yield seed. 104 Most horticulturists 

 look at the great size and anomalous development of the fruit as the 

 cause, and sterility as the result ; but the opposite view, as we shall 

 presently see, is more probable. 



Sterility from i ssive development of tlie organs of Growth or 



Vegetation, — Plants which from any cause grow too luxuriantly, and 

 produce leaves, stems, runners, suckers, tubers, bulbs, &c.,in excess, 

 sometimes do not flower, or if they flower do not yield seed. To 

 make European vegetables under the hot climate of India yield 

 seed, it is necessary to check their growth; and, when one-third 

 grown, they are taken up, and their stems and tap-roots are cut or 



101 ' Gardener's Chronicle,' 1843, p. 'Races of Man;' Gallesio, 'Teoria 

 628. In this article I suggested the dellaRiproduzione,'18I6,pp.l0l-110. 



theory above given on the doubleness Meyen (' Reise um Erde,' Th. ii. s. 



o*.' flowers. This view is adopted by 214) states that at Manilla one 



Carriere, 'Production et Fix. des variety of the banana is full of seeds: 



Varietcs.' 1865, p. 67. and Chamisso (Hooker's ' Eot. Misc.,' 



102 Quoted by Gartner, ' Bastarder- vol. i. p. 310) describes a variety of 

 gengung,' s. 567. the bread-fruit in the Mariana islands 



103 ' Gardener's Chronicle,' 1866, p. with small fruit, containing seeds 

 901. which are frequentlv perfect. Burnes. 



104 Lindley, ' Theory of Horticul- in his ' Travels in Bokhara,' remarks 

 ture.' pp. 170-1 79 ; Godron, • De l'Es- on the pomegranate seeding in Mazen* 

 pece,' torn. ii. p. 106; Pickering, deran, as a remarkable peculiarity. 



