INTRODUCTION. 5 
materials suitable to their organization, which are taken up and distributed 
by vessels, which do not correspond, however, except that those of plants 
may be considered similar to the alimentary canal of animals. In certain 
plants, as in Chelidonium and Vallisneria, a kind of circulation has been 
observed. 
A still greater relation appears in the propagation of animals and plants, 
which frequently takes place in both kingdoms by means of spontaneous 
division, and the growth of the separating shoots or buds, as in the case of 
the creeping roots, and the shoots of many plants ; and also in some animals, 
where numerous stems united by a common base, give rise to others 
which become separated and commence an independent existence, as in the 
polypi. The spontaneous division of the infusoria belongs to this mode of 
reproduction. Plant and animal eggs can also be brought into comparison 
with each other, if the lower orders of both be taken for this purpose. The 
phenomena of vegetable life which are also present in the animal kingdom, 
may be stated as follows : 
1. The ability of individual portions when detached to grow and live 
independently, and even to originate others. Many plants can be increased 
by cuttings, and it is well known that pieces cut from fresh water polypi 
will grow and form perfect individuals. 
2. As plants always produce new shoots, so in the corals are similar parts 
produced ; and as a tree placed with its top in the ground may produce 
leaves and blossoms from the upturned roots, so the base of a sertularia 
may become the head by producing young polyps. 
3. The formation of buds happens in both kingdoms, of which the polypi 
again afford examples. 
4. In plants we also find traces of irritability, like the movements of the 
mustard plant when touched. Animals and plants are both subject to 
sleeping and waking. 
5. Plants and animals undergo metamorphosis, and sustain malformation 
and disease, which sooner or later result in death, after which both are subject 
to fermentation and putrefaction. 
6. Plants and animals, and their organs, are developed gradually according 
to a certain plan. As the root and stem are formed out of the seed, and the 
leaves from the cotyledons, until at length the flower and its component 
parts are produced, so we find the several organs of the animal body to be 
formed from the membrane of the yolk. 
7. As there are plants which live but a few days, or even hours, like 
many fungi, so there are animals, as the ephemera. Most plants, like most 
insects, live but a single summer. On the other hand, plants as well as 
animals may attain a very great age, and examples are not rare of trees a 
thousand years old. Animals also become very old, although it is difficult 
to arrive at any certain conclusion upon this point. There is reason to 
believe that the crevish or river crab (Astacus) lives about twenty years ; 
the honey bee ten years ; the pike several centuries ; carps.and eels acentury ; 
crocodiles and tortoises, whose growth continues during a long period, 
probably attain a very great age ; a toad was. watched in a house for thirty- 
ICONOGRAPHIC ENCYCLOPADIA.—VOL II. 14 299 
