438 BOTANY. 



538. The tissues of the fundamental system in the An- 

 giosperms are, in general, sharply set off from those of 

 the epidermal and fibre-vascular systems. In the annual 

 stemmed species the fundamental tissues constitute the great- 

 er part of the stems, but in perennial-stemmed species there 

 is proportionately less of these, and more of the fibro- vascular 

 tissues ; in the former the principal tissue in the funda- 

 mental system is parenchyma, which occupies the interfascic- 

 ular spaces, as well as the greater part of that lying between 

 the bundles and the epidermis i.e., in the cortical region. 

 In perennials, on the contrary, the interfascicular spaces are 

 in many cases occupied by sclerenchyma, and the cortical 

 region either entirely disappears (as in Dicotyledons) or it 

 becomes filled with sclerenchymatous or fibrous tissue. 



In the leaves the fundamental system rarely includes more 

 than chlorophyll-bearing parenchyma, while in the parts of 

 flowers a similar tissue is found, which is, however, generally 

 wanting in chlorophyll. The succulent parts of fruits, 

 whether phyllome or caulome structures, are composed of 

 parenchyma of the fundamental system. 



539. 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 presents more or less distinctly 

 two sides, viz., xylem and phloem. Each of these sides, as 

 previously described (paragraph 147), generally contains 

 parenchymatous, fibrous, and vascular tissues, the latter 

 tracheary in the xylem, and sieve in the phloem. 



54O. 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. In 

 Fig. 314 there pass down from each leaf three bundles ; 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 bundles from the lower 



