Page:An introduction to physiological and systematical botany (1st edition).djvu/134

 104 of the succeeding winter, nor can any artificial heat preserve them. This is, no doubt, to be attributed to the exhaustion of their vital energy by flowering. Several plants of hot climates, naturally perennial and even shrubby, become annual in our gardens, as the Tropæolum, Garden Nasturtium.

In the Turnip, and sometimes the Carrot, Parsnep, &c., the Caudex or body of the root is above-ground and bare, becoming as it were a stem. Linnæus indeed calls the stems of trees "roots above-ground;" but this seems paradoxical and scarcely correct. Perhaps it would be more accurate to say the caudex is a subterraneous stem; but we rather presume it has functions distinct from the stem, analogous, as has been hinted p. 55, to digestion, at least in those plants whose stems are annual though their roots are perennial.

The fibres of the root, particularly those extremities of them which imbibe nourishment from the earth, are in every case strictly annual. During the winter, or torpid season of the year, the powers of roots lie