GROUPS OF TISSUES,-OR TISSUE-S. STEMS. 47 
this and allied species the bundles are curiously isolated 
from the surrounding ground-tissues of the stem. 
88. The fibro-vascular bundle of the underground stem 
of the common Brake-fern (Pteris) is composed of trache- 
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Fia. 30.—Magnified cross-section of the stem of a smaller Club-moss (Selagi- 
nella inzequifolia), showing three bundles. 
ary, sieve, and soft tissues and a small amount of poorly 
developed fibrous tissue. In transverse section the bundle 
has usually an elliptical outline. The great mass of the 
bundle is made up of large scalariform vessels, which 
occupy its interior (9, 9,9, Fig. 31). Enclosed in the sca- 
