REJUVENESCENCE IN NATURE. 67 



unmistakeable that the leaf-formations take three succes- 

 sive onward flights {Aufschoiinge) in the course of the 

 metamorphosis : one in the stock or body of the plant, 

 one in the flower, and, finally, the last in the fruit. A 

 close investigation of this phenomenon shows, that there 

 are also subordinate risings and sinkings even within the 

 first and second regions of elevation. 



If we examine, in the first place, in reference to this 

 point, the conditions of breadth of the base of the leaf, 

 we find on the stock or stem of the plant, from the first 

 to the last of its leaves, a decrease, sometimes gradual 

 and sometimes taking place by starts, and this decrease 

 is indeed so constant, that perhaps every exception might 

 be traced to the phenomenon of retrogressive metamor- 

 phosis examined above, although it is not equally obvious 

 in all.* But with the advent of the flower a new increase 

 of the breadth of the base of the leaf frequently occurs, 

 the sepals exhibiting a broader base than the highest 



development of the fruit consequent on fertilisation as a pathological con- 

 dition, a disease. (!) 'Essai de r^duire la Physiologie veg^tale a des 

 principes fondatnentaux,' 1828, pp. 33, 38.) 



* Among these exceptions is the condition of the cotyledons in the 

 numerous dicotyledonous plants in which the opposite half-embracing 

 cotyledons or seed-leaves are succeeded by alternate, more extensively em- 

 bracing euphyllary-leaves, or wholly or almost wholly embracing cataphyllary- 

 leaves, which latter is the case, for instance, in Asarum. In the mono- 

 cotyledons, on the contrary, the seed-leaf is always completely amplexicaul. 

 There appears, moreover, a strange case in Convallaria majalis, in which a 

 number of cataphyllary-leaves forming closed sheaths, are followed by one 

 which is only two thirds embracing, (the same which bears the inflorescence 

 in its axil), and this is succeeded by two euphyllary-leaves, which are again 

 completely amplexicaul. Crocus luhus, also, and other species of this genus, 

 exhioit a strange aberrant condition to be mentioned in connection with the 

 foregoing. A number of completely embracing cataphyllary-leaves, closed 

 round into tubes, are succeeded by euphyllary-leaves, mostly arranged 

 according to the % position, the sheath-like basilar portions of which are 

 not closed into tubes, but are confluent together one with another in the 

 direction of the longitudinal path of the line of arrangement of the leaves, 

 (the spiral line cutting through the points of origin of the successive leaves), 

 whence arises as it were a single connected spiral sheath common to all the 

 euphyllary-leaves. The breadth of the base of a single leaf consequently 

 amounts here to % of the circumference of the stem. These are foUowed 

 by hypsophyllary leaves preceding the terminal flower, the first closed into 

 a tube, like the cataphyllary-leaves, the second, on the contrary, open, 

 and only imperfectly embracing the stem. 



