. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. 112 MINUTE STRUCTURE OF THE HOOT. duccd to a single duct, as iu some Carices, or there maj- be a large duct surrounded by smaller ones with or without inter- vening cells, or many large and small ducts variously conjoined. Moreover, there are all degrees of compactness in the union of the different bundles of woody tissue with each other. 339. The cribrose part of the bundle may be reduced to a single cribrose tube (, Anacharis), or two or three (e. ff., Po
. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. 112 MINUTE STRUCTURE OF THE HOOT. duccd to a single duct, as iu some Carices, or there maj- be a large duct surrounded by smaller ones with or without inter- vening cells, or many large and small ducts variously conjoined. Moreover, there are all degrees of compactness in the union of the different bundles of woody tissue with each other. 339. The cribrose part of the bundle may be reduced to a single cribrose tube (, Anacharis), or two or three (e. ff., Pon- tederia) ; but usually there are mauj-, which maj' be variously disposed. 340. Bast-fibres may be associated with the cribrose-oells in the primary structure of the root, and they may be scattered (and occasionallj- with some sclerotic parenchjma) in the cortex. In Philodeudrcm these scattered groups of bast-Iibres frequently contain oleo-resin canals. Secondary Structure. 341. The older parts of roots, even the recently formed por- tions lying just back of the root-hairs, may undergo changes either b}' the alteration of their existing tissue elements or by the in- troduction of new ele- ments. Some roots, however, do not suffer much change fiom first to last. Their cells may become more strongly cutinized or lignified as the case maj' be, but no new elements are brought in. This is true of the i-oots of man3- monocotyledons, but in dicotyledons the secondarj- changes are generall}' verj' marked. The changes maj- af- fect either the I'ortex or the central cylinder; in some cases the former more than the latter. Soctioii Hirougli tlioceiUralcyliri'lerofabinary root of avascular cryptogam (Cyatbeameilullaris): <?, iniernal layer of the proper cortex; p, eiuiodermis; m, pe- ripheral layer of the cyliiuler; I, llbor fasci^jles; r, woody fascicle; c, conjunctive paren- chyma (pith and medullary rays). (Van Tieghcm.). 93. Please note that these images are extracted fro
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