INTRODUCTION. 9 
tracting on the application of an external stimulus, termed 
_ Irrrrasmaity. This property is found in parts of some 
plants. But no locomotive power is observed in them. 
23. As a general distinction, the concise definition’ by 
Linnezus is admirable, “ Minerals grow; Vegetables grow 
and live; .Animals grow, live, and have feeling.” These 
differences, so well marked in the higher orders of each, as 
a Tren, a Man, disappear in the lower grades, where the — 
animal and vegetable kingdoms approximate, and it is often 
very difficult to distinguish them from each other. It7is thus 
impossible to give diagnostic marks between these two great 
divisions of animate nature, which shall include all the genera, 
because some of the tribes resemble each other so much. 
They meet at the lower series of the scale in each, and 
pass insensibly into each other. Many of the Polypi are en- 
tirely destitute of the power of voluntary motion, and would 
appear to be almost destitute of sensation; while some of 
_ the lower tribes of Algw, as the Oscillatorie, possess — i 
_ Ddility in so high a degree that some have pro 
them in the animal kingdom. The Polypi vaginanti were 
placed among vegetables in Tournefort’s arrangement; and 
Sponges are considered as animals by some, while others re- 
gard them as plants. Lately, some species of Conferve, 
formerly regarded as plants, have been removed from vege- 
tables and placed among the simplest tribes of the animal 
kingdom, by the eminent naturalist, Bory de St. Vincent. 
_ It has been conjectured that there are particular forms of 
organic germs which can produce either animals or vege- 
tables. Some cryptogamic botanists hold the singular doc- 
trine, that in some instances, metamorphoses of plants inte. 
crystalline texture. — eg 
eaeeemd of —— eens oceurs voy in 
animals, and of these animals into plants again, occasionally 
_ take place. And Agardh threw out the conjecture, that 
the mineral kingdom approaches the other two classes of __ 
Asture, in some of the simpler Algz, which have et one 
