PRELIMINARY DISCOURSES. Xxl 



When a plant is full-grown, or sufficiently matured to bloom, a 

 striking change takes place. Slender branches are often thrown out, 

 or the internodes near the summit of the stem become suddenly 

 elongated ; there is usually, also, a great diminution observable in 

 the size and frequently an entire change in the outline, or figure 

 of the foliage, on the flowering branches. Next we find, in many 

 instances, a sort of transition leaves, called bracts, in the immediate 

 vicinity of the flowers. These bracts are sometimes scarcely changed, 

 in appearance, from the other leaves on the stem and branches ; but 

 we find them, occasionally, assuming the hue, and almost the tex- 

 ture, of petals. Having thus ascertained that bracts are nothing 

 more than modified leaves, we now approach the flower, itself, 

 which is always the termination, or concluding development, of a 

 stem, or branch;* and here we find, in many plants, a whorl of 

 green leaflets (or sepals composing what is called the calyx,} at the 

 base of the flower, so little altered from the small leaves immediate- 

 ly below, that we have no hesitation in considering them as of 

 precisely the same nature; the only difference being, that, by the 

 suppression of internodes, they are arranged in a ring (called a 

 verticil, or whorl,) at the summit of the peduncle, or ultimate branch 

 of the flower-stalk. This is the regular mode of arrangement, of all 

 the parts of a flower. The sepals, petals, stamens and even the 

 pistils, in symmetrical flowers (i. e. when all the parts, which normally 

 belong to them, are present) are all disposed in a succession of 

 verticils. In the flowers of the DICOTYLEDONS, or Exogenous Plants, 

 each floral verticil, when complete, is composed of five modified 

 leaves or some multiple of that number. It may and often does 

 vary from this, by reason of a suppression of some of the parts ; but 

 five is the normal, or what may be termed the constitutional number, 

 in the floral verticils of that great division of the vegetable king- 

 kinds according as the rascular and fibrous, or the cellular, tissue predominate?. 

 In the one case, we have dry, skinny, woody, or even bony, seedvessels; and in 

 the other, we find the product to be Qeshy, pulpy and succulent fruits. Even in 

 the same pericarp, we often see one portion tender and juicy, while another 

 portion is parchment-like, or bony; as in pomes, and drupes or apples and 

 cherries. It is only necessary to extend and apply this doctrine to all the modified 

 organs of plants and to keep the idea constantly in mind in order to compre- 

 hend the whole mystery of metamorphosis. 



* Although, for convenience in descriptive phraseology, we often say that flowers 

 are lateral, axillary, sessile, Ac., it should, nevertheless, be constantly borne in 

 mind, that a flower is always the terminal and crowning development as the 

 fruit is the final product -of a stem, or branch; that the pedicels of aggregated 

 florets are the ultimate ramifications of the main flowering stalk, and that wheu 

 a flower appears to be sessile, it is merely by the suppression more or less com* 

 pletc of the internode which normally constitutes its proper peduncle. 



