238 BOTANY. 



Qc) Observe the large early flowers of violets, which are dependent 

 upon insects for pollination. Notice that after a while none of these 

 appear, but only small ones destitute of petals. In the common yel- 

 low violet these are borne on the stem above the ground, but in blue 

 violets they are often underground. These small flowers are self- 

 pollinated (cleistogamous). 



605. The fibro-vascular bundles of the stems of Angio- 

 sperms are entirely of De Bary's "collateral" class; that 

 is, each bundle in cross-section is more or less distinctly 

 two-sided, viz., wood and bark. Each of these sides gen- 

 erally contains soft, fibrous, and vascular tissues. 



506. The disposition of the bundles in the Angiosperms 

 is for the most part dependent upon the position of the 

 leaves. Nearly all the first-formed bundles are of the kind 

 termed "common bundles;" that is, they extend on the 

 one hand into the leaf, and on the other down into the 

 stem. 



507. The general arrangement may be illustrated by Pig. 

 134, in which there pass down from each leaf three bun- 

 dles; at the lower internode these are, on the left, a, b, c, 

 and, on the right, d, e, f. At the next internode, where 

 the leaves stand at right angles to the lower ones, there 

 are three bundles again, g, h, i, and k, I, m; these are 

 largest at their points of curvature, and they dwindle in 

 size as they pass downward and finally unite with the bun- 

 dles from the lower pair of leaves. The bundles from the 

 third internode pass downward, and in like manner join 

 those from the second pair of leaves, and so on. Thus in 

 such a stem every bundle passes downward through one 

 internode before joining another, and in any internode all 

 the bundles are derived from the leaves at its summit. 



508. In some Angiosperms the bundles in a cross-section 

 of a stem are separate from one another, while in others 



