REJUVENESCENCE IN NATURE. 43 



the longer maintenance of the hybrid form is effected by 

 a sprout-formation, not merely inessential in the sense 

 above denoted, but also quite extraordinary, and alto- 

 gether absent in the parents of the hybrid. 



To these indications respecting the connection of the 

 inessential sprouts with the economy of vegetable life, we 

 have to add also the consideration of certain cases, which 

 completely remove the sharpness of the former distinction, 

 since, as cases of transition, they may be taken in two ways. 

 In contrast to the essential sprouts, which, as determinate 

 series of subordinate generations in which the metamor- 

 phosis of the plant is carried to its term, represent, 

 according to number, a firmly fixed system of axes, each 

 successive one bringing something new we have called 

 the inessential sprouts, lying outside the series and inde- 

 finite in number, repetition-generations. But cases occur 

 of real repetition-generations, which do not lie outside 

 the line, but belong to the series of transition generations 

 necessary to the attainment of the goal. Here refer the 

 strengthening generations already noticed above* of 

 many perennial plants, which in the first year are still too 

 weakly to form flowers and fruit. The fortification to 

 the point of fruitfulness may occur either in the next 

 succeeding generation, otherwise essentially like the first, 

 or deviating only in a retrogression to cataphyllary leaf- 

 formation, and thus in the second year, if every gene- 

 ration is destined to a year's duration, or, more or less 

 numerous, and then mostly numerically indeterminate, 

 in all essentials completely similar generations, may suc- 

 ceed one another, till at length that age of the " stock" 

 is attained in which it advances to the formation of 

 blossom. The latter condition occurs especially frequently 

 in trees, and indeed most distinctly in those which have 

 no terminal buds, and consequently, in the strictest sense, 

 unfold each new year a generation composed of un- 

 doubtedly new individuals (evident lateral buds). Three 



* Sec pp. 29, 30. 



