CASES SIMULATING ALTERNATION OF GENEllATIONS. 221 



X. 



CASES SIMULATING ALTERNATION OF 

 GENERATIONS. 



§ 1. In connection with the subject of alternation of gene- 

 rations, a short reference may be made here to various 

 cases, which, without being really of the same nature, have 

 some apparent resemblance to it, or have for some reason 

 been confounded with it. 



Most properly the expression is used to imply a certain 

 regularity of recurrence of sexless and sexual forms in tlie 

 succession of progeny, and a certain diversity in their 

 general character. It cannot be regarded as a proper case 

 of alternation of generations, when the interchange of the 

 two modes of propagation is casual and not a fixed cha- 

 racter of the species — as may be the case, for instance, in 

 plants with bulbiferous stems or viviparous flowers, which 

 propagate by gemmae in seasons when they cannot mature 

 their seeds. 



§ 2. Nor again does an interchange of different modes 

 of budding belong to the class of cases we have been con- 

 sidering, for this would be an alternation of peminatiotis 

 rather than of generations. Instances of such a kind occur 

 in the alternation of attached and deciduous buds in plants. 

 Thus a grass raised from one of the bulbils thrown off by a 

 deciduous infloresence multiplies its stems into a large 

 tussock by a succession of leaf-shoots which vegetate in 

 connection with the primary axis, and may all bear gemmi- 

 parous flowers, like that which furnished the original de- 

 ciduous gemma. 



