Trunks and Props. 199 



directions ; others are carried by the birds, sheep, clothes of men, 

 &c. ; others again are. provided with balloons to transport them 

 away from their parent soil, to settle in new countries ; others 

 with wings, &c. Fig. 31 shows a winged seed, A the seed, B 

 the wing. Fig. 34, a seed crowned with a pappus ; A the seed, 

 B the stipes of the pappus, c d a feathery pappus. Fig. 39, a 

 seed crowned with a calyculus ; A the seed, B the calyculus. 



Trunks and Props, 



Lindley observes, that when a plant begins to grow from the 

 seed, it is a little body called an embryo, with two opposite ex- 

 tremities, of which the one elongates in the direction of the 

 earth's centre, and the other, taking a direction exactly the con- 

 trary, extends upwards into the air. This disposition to develope 

 in two diametrically opposite directions, is found in all seeds 

 properly so called, there being no known exception to it, and the 

 tendency is moreover so powerful that no external influence is 

 sufficient to overcome it. The result of this development is the 

 axis or centre round which the leaves and other appendages are 

 arranged. That part of the axis which forces its way down- 

 wards, constantly avoiding the light, and withdrawing from the 

 influence of the air, is the root, which we have mentioned be- 

 fore ; and that which seeks the light, constantly exposing itself 

 to the influence, and expanding to the utmost extent of its nature 

 to the solar rays, is the ascending axis or stem. As the double 

 elongation, just mentioned, exists in all plants, it follows that they 

 must have necessarily at an early period of their existence at 

 least, both stem and root ; and that, consequently, when plants 

 are said to be rootless, or stemless, such expressions are not to 

 be considered physiologically correct. The stem has received 

 many names, such as caudex ascendens, caudex intermedius, 

 culmus, stipes, truncus, and truncus ascendens. It always 

 consists of bundles of vascular and woody tissue, embedded in 

 cellular substances in various ways, and the whole enclosed 

 within a cuticle. When the stem and root, or the ascending and 

 descending axis diverge, there commences in many plants a dif- 



