REJUVENESCENCE IN NATURE. 29 



occurs especially when the sprout is destined to be sub- 

 sequently developed into the central shoot. Thus many 

 lilies exhibit in the axils of the euphyllary leaves cata- 

 phyllary buds, which finally fall off as bulbels, and con- 

 tinue their development in the following year ; so also 

 we see the buds formed in the axils of the euphyllary 

 leaves of most trees, intended to overlast the winter and 

 unfold in the next year, commence with cataphyllary 

 structures. In many instances the plant first reaches the 

 lowest stage of its metamorphoses by such a retrogression, 

 the lateral sprout going down to a lower rudiment than 

 the main or original sprout brought forth by the seed. 

 This is a process through which the plant enters more 

 closely into connexion with the earth in the second 

 generation than in the first, and becomes more firmly 

 established in it, preparing a more fixed, enduring and 

 sheltered existence, to the vegetable life, though its cata- 

 phyllary formation and the adventitious roots mostly fol- 

 lowing this. The following remarks may serve to illus- 

 trate this case, which is especially important in reference 

 to the biology of perennial herbaceous plants. It is self- 

 evident that the cotyledons of Dicotyledonous plants, 

 although mostly strikingly different * in shape from all 

 the following leaves, do not belong to the lowest leaf- 

 formation, but rather bear, essentially, the characters of 

 the second leaf-formation, that of the euphyllary leaves ; 

 while, on the other hand, the sheath-like cotyledon of the 

 Monocotyledons is mostly decidedly like a cataphyllary 

 leaf. Now Dicotyledons continue the euphyllary forma- 

 tion directly from the cotyledons, without ever producing 

 cataphyllary leaves either on the main or the lateral 

 sprouts; perennial Dicotyledons, on the other hand, 

 mostly descend from the original leafiness to cataphyllary 

 formation, and this either on the main sprout itself, as in 

 Adoxa, Helleborus niger, liepatica, and Anemone nemo- 



* The first leaves of the sprouts have been compared with the cotyledons 

 of the main sprout, a ground for which is indeed to be found in their position, 

 but only rarely in their forms. 



