. A textbook of botany for colleges and universities ... Botany. STEMS 699 The influence of external factors upon tnecfaanical tissues. — Mechan- ical stimuli. — An unattached tendril has less tensile strength than one that is attached, the latter sometimes being two to iive times stronger than the former. Frequently this change in tensile strength is associated with a structural change, more mechanical cells being developed or further wall thickening appearing in those already present (figs. 1023-1026). In some cases coUenchyma develops into bast upon the attachment of the tendril. It has bee
. A textbook of botany for colleges and universities ... Botany. STEMS 699 The influence of external factors upon tnecfaanical tissues. — Mechan- ical stimuli. — An unattached tendril has less tensile strength than one that is attached, the latter sometimes being two to iive times stronger than the former. Frequently this change in tensile strength is associated with a structural change, more mechanical cells being developed or further wall thickening appearing in those already present (figs. 1023-1026). In some cases coUenchyma develops into bast upon the attachment of the tendril. It has been claimed that growing stems of Helleborus sub- jected to tension develop bast in regions where ordinarily none is pres- ent; furthermore, stems subjected to tension for three days have been found able to support a weight of 3500 grams, ,.1 ^ ^1 • ,• Figs. 102^-1026. — Cross sections of tendrils of Cvc/an- while at the mception ,, ^, , ,. .. .. , ^ tkera expioaens: 1023, a diagrammatic cross section of of the experiment only 400 grams could be sup-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Coulter, John Merle, 1851-1928; Barnes, Charles Reid, 1858-1910, joint author; Cowles, Henry Chandler, 1869- joint author. New York, Cincinnati [etc] American book company
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