4 THE PHENOMENON OF 



nescence. is either morphological, the structure returning 

 actually from a higher stage into a lower formation ; as 

 we see, for example, in annual Rejuvenescence of many 

 herbaceous perennials (plantae redivivte), as also in most 

 woody plants, in the buds, which commence the rejuve- 

 nised course of life with leaves of the lowest stage of 

 formation, the bud-scales belonging to the "cataphyllary" 

 (meder-blatt) formation ;* or the retrogression is merely 

 physiological, a chemical decomposition and dissolution 

 in the structure already existent, whereby this becomes 

 capable of a Rejuvenescence of its form, combined with a 

 more or less distinct metamorphosis. Such it is in the 

 interchange of materials in animals, with which are con- 

 nected their more gradual and imperceptible, as well as 

 the more sudden and surprising transformations. That 

 the like is not wanting in plants, will be demonstrated 

 in the succeeding examination of the phenomena of 

 Rejuvenescence in Cell-life. 



"We have consequently to distinguish a descending and 

 an ascending direction in the Rejuvenescence, one retro- 

 gressive, the other advancing with new impetus, one 

 undoing the old and existent, the other shaping out the 

 new. Both directions are necessarily related to that 

 renewal of the vital movement to which we have applied 

 the term <c Rejuvenescence," and it is their alternation 

 which maintains life in vibration and guards it against 

 untimely rest. The smaller the vibrations in which it 

 occurs, the more constant will the formative process 

 appear to be, as for example in the processes completing 

 the structure of a cell not destined to division ; but even 



* There arises great difficulty in rendering these terms applied to the 

 different orders of leaves, since we have none corresponding to them in 

 English. They are so frequently used, not only in a substantive but an 

 adjective way, both in this treatise and in other recent German works, and 

 have such a definite meaning, that we venture to invent new words and to 

 use them in this translation. The word " nieder-blatt" (lower leaf), signifying 

 cotyledons, the bud-scales at the base of branches, or the scales of rhizomes, 

 is rendered by cataphyll; " laub-blatt" (leafy-leaf), stem leaves generally, by 

 euphyll; " hoch-blatt" (high leaf), leaves belonging to the inflorescence, by 

 hysophyll. A. H. 



