Chap. XVIII. OF THE ORGANS OF VEGETATION. 153 



mutilated. 105 So it is with hybrids; for instance, Prof. Lecoq 106 had 

 three plants of Mirabilis, which, though they grew luxuriantly and 

 flowered, were quite sterile ; but after beating one with a stick until 

 a few branches alone were left, these at once yielded good seed. The 

 sugar-cane, which grows vigorously and produces a large supply of 

 succulent stems, never, according to various observers, bears seed in 

 the West Indies, Malaga, India, Cochin China, Mauritius, or the 

 Malay Archipelago. 107 Plants which produce a large number of 

 tubers are apt to be sterile, as occurs, to a certain extent, with the 

 common potato; and Mr. Fortune informs me that the sweet 

 potato {Convolvulus batatas) in China never, as far as he has seen, 

 yields seed. Dr. Eoyle remarks 108 that in India the Agave vivipara, 

 when grown in rich soil, invariably produces bulbs, but no seeds ; 

 whilst a poor soil and dry climate lead to an opposite result. In 

 China, according to Mr. Fortune, an extraordinary number of little 

 bulbs are developed in the axils of the leaves of the yam, and this 

 plant does not bear seed. Whether in these cases, as in those of 

 double flowers and seedless fruit, sexual sterility from changed 

 conditions of life is the primary cause which leads to the excessive 

 development of the organs of vegetation, is doubtful ; though some 

 evidence might be advanced in favour of this view. It is perhaps a 

 more probable view that plants which propagate themselves largely 

 by one method, namely by buds, have not sufficient vital power or 

 organised matter for the other method of sexual generation. 



Several distinguished botanists and good practical judges believe 

 that long-continued propagation by cuttings, runners, tubers, bulbs, 

 &c, independently of any excessive development of these parts, is 

 the cause of many plants failing to produce flowers, or producing 

 only barren flowers, — it is as if they had lost the habit of sexual 

 generation. 109 That many plants when thus propagated are sterile 

 there can be no doubt, but as to whether the long continuance of this 

 form of propagation is the actual cause of their sterility, I will not 

 venture, from the want of sufficient evidence, to express an opinion. 



That plants may be propagated for long periods by buds, without 

 the aid of sexual generation, we may safely infer from this being the 

 case with many plants which must have long survived in a state of 

 nature. As I have had occasion before to allude to this subject, I 

 will here give such cases as I have collected. Many alpine plants 



io5 Ingledew, in ' Transact, of Agri- several species indigenous in Mauri- 

 cult, and Hort. Soc. of India,' vol. ii. tius. 



106 'De la Fecondation,' 1862, p. 1(/8 'Transact. Linn. Soc.,' vol. xvii. 

 S08, p. 563. 



107 Hooker's 'Bot. Misc.,' vol. i. p. 10D Godron, ' De l'Espece,' torn. ii. 

 99; Gallesio, 'Teoria della Ripro- p. 106 ; Herbert on Crocus, in ' Jour- 

 duzione,'p. 110. Dr. J. de Cordernoy, nal of Hort. Soc.,' vol. i., 1816, p. 

 in 'Transact, of the R. Soc. of Mauri- 254: Dr. Wight, from what he has 

 tius' (new series), vol. vi. 1873, pp. seen in India, believes in this view ; 

 60-67, gives a lai ge number of cases ' Madras Journal of Lit. and Science,' 

 of plants which never seed, including vol. iv., 1836, p. 81. 



