INTRODUCTION". 5 



materials suitable to their organization, which are taken np 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 

 jDolypi. 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 nroduce 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 afltbrd 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 a century ; 

 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 ENCYCLOPEDIA. — VOL II. 14 209 



