KKJUVENESCENCE IN NATURE. 189 



envelopes obstructing the further development or reju- 

 venised formative action, sueh as we have here examined 

 in the life of the cell, are repeated in the compound 

 organism of the plant. Thus we see that the first leaves 

 and roots of Marsilia and Pilularia break through the 

 tissue of the proembryo, the first roots of most of the 

 Monocotyledons, as well as all the subsequently appearing 

 adventitious roots, through the cortical tissue of the stem. 

 The leaves of Ophioc/lossum break through the cellular 

 cover under which they are formed ; the young sporange 

 of ttie Hepaticse breaks through its outer coat above, 

 leaving it behind as a sheath at the base ; the sporange of 

 the Mosses tears it in two at the base, and lifts it up as 

 the calyptra. In like manner many Agarics tear open the 

 veil which encloses them in their young stage. The bark 

 of many trees exhibits a process of peeling otf. We 

 find a periodical exfoliation of the periderm in Bubus 

 odoratus, Spiraa opulifolia, and particularly distinct in 

 the Birch and the Strawberry-tree {Arbutus Andrachne); 

 a peeling of the outer liber-layers in the Vine and 

 Clematis ; a scaling-ofi" of the bark in the Plane, the 

 Apple, the Fir, &c. The tuberous stem of Isuetes 

 scales off" at its circumference. Finally, the emergence 

 of the embryo fi'om the seed-coats in the germination of 

 Flowering plants, presents itself as a complete " slipping 

 out." 



We now pass to another mode, in which cell- 

 structure advancing to a rejuvenised vital activity frees 

 itself from the envelopes previously formed by itself, 

 namely, to the phenomena of chemical softening and 

 solution of the cell-membrane, which take place some- 

 times as a swelling-up, terminating in dissolution, and 

 sometimes as an imperceptible resorption. The change 

 of the cell-membrane into a more or less fluid jelly 

 which is at length wholly dissipated, at the advent of the 

 series of generations, is a very frequent phenomenon 

 among the lowest groups of the Algte, as, for instance, m 



