Excerpt from Abscission of Flowers and Fruits in the Solanaceae, With Special Reference to Nicotiana: A Thesis Submitted in Partial Satisfaction of the Requirements for the Degree of Doctor of Philosophy at the University of California Although it is a matter of common observation that many plants are capable of detaching portions of the body, the underlying cause and the actual mechanism which bring about such separation are only slightly understood. The process has often been described as' One Of self-pruning by which the plant rids itself of useless portions of its body. Since abscission is sometimes confused with exfoliation, it seems desirable here to distinguish definitely between these two phenomena. It can be said that, in general, exfoliation is preceded by drying and death of the part to be cast off and that actual separa tion of the organ is accomplished by a mechanical break through dry, dead tissues. Abscission, on the other hand, is usually not preceded by drying and death of the organ concerned and its detachment is accomplished by a separation along the plane of the middle lamellae of active living cells. Abscission may be either axial or lateral. Axial abscission includes the abscission of portions of stems, shoots, entire flowers or fruits. Lateral abscission includes the abscission of leaves, petioles, sepals, petals or styles. Considerable attention has been given by investi gators to the abscission of flowers because of the theoretical detriment to crops caused by the fall of the flower before the fruit is formed. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

A THESIS SUBEUTTED IN PARTIAL SATISFACTION OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY AT THE UNIVERSITY OF CALIFORNIA BY JOHN NORMAN KENDALL UNIVERSITY OF CALIFORNIA PUBLICATIONS IN BOTANY Vol . 5. No . 12. pp . 347.428. 10 text figs.. plates 49-53 Match 6. 1918 . ABSCISSION OF FLOWERS AND FRUITS IN THE SOLANACEAE. WITH SPECIAL REFER, ENCE TO ATICOZYAXA BY JOHK N . KEXDALL CONTEXTS I . Iutrodootion ..................................................................................... 348 11 . Summary of the literature ......-.........-.... ...... . ....................................... 350 IT1 . Technique . ................................ 361 TV . nistology and cytology of the pedioel ........................................................ 363 1 . Hjstological and cytological condition of thc mature pedieel ...... 363 2 . Development of the soparation eoue in Nicotiosa and Lycopet- . . simm - .................................................................................................... 367 3 . Increase in size ancl development of mechanical tissue in the pedicel of Nicotiana and Lgcopersicum . 369 8 . The process of abrrelssiou ............................................................................ 371 1 . General description of the proeesa in several genera .................... 371 2 . Method of cell separation .................................................................. 376 V3 . Abscission of the style and corolla 383 VII . Time of abscission ............................................................................................ 385 1 . Roaction time ........................................................................................ 385 2 . Abscission tiuie ...................................................................................... 396 V111 . Experimental intluetion of abscission . 397 1 . Induction by ilIuminating gas 397 2 . Action of aoids on the separation layer of Nicotiona .................. 404 3 . Tntluction by mechanical injury 406 4 . The ability of certain species to throw off yerlicels from which all the floral organs havo been rcmoved, as related to the induction af abscission by nechauic.al injury 410 IX . Summary ........................................................................................... 411 X . Conclusion .............................................................................................. 415 XI . Literature oited 418 . Plates ...........................................A 420 348 l, n.iversity of California Publieot.wns in Botathy VOL. 5 INTRODUCTION Although it is a matter of common observation that many plants arc capable of detaching portions of the body, the underlying cause and the actual mechanism which bring about such separation are only slightly understood. The process has often been described asv ke of self-pruning by which the plant rids itself of useless portions of its body. Since abscission is somctimes confused with exfoliation, it seems desirable here to distinguish definitely between thme two phenomena. It can BC said that, in general, exfoliation is preccded by drying and death of the part to be cast off and that actual separa- tion of the organ is accomplished by a mechanical break through dry, dead tissues. Abscission, on the other hand, is usually not preceded by drying and death of the organ concerned and its detachment is accomplished by a separation along thc plane of the middle lamellae of active living cells. Abscission may he either axial or lateral. Axial abscission includes the abscission of portions of stems, shook, entire flowem or fruits. Lateral abscission includes the abskssion of lcavcs, petioks, sepals, pctah or styles..

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