﻿ABSCISSION IN MIRABILIS JALAPA 



Francis E. Lloyd 

 (WITH PLATE XIII AND TWO FIGURES) 



The purpose of this investigation 



Although the phenomenon of abscission has received no small 

 amount of attention, a study of the literature fails to discover any 

 real uniformity of opinion as to the precise steps involved. This 

 divergence I have already indicated in an earlier paper. 1 As I 

 shall take occasion at a future time to attempt a general critique 

 of the whole subject, my present purpose is a restricted one, 

 namely, the consideration of a more recently published account of 

 abscission in the common "four o'clock" (Mirabilis jalapa), by 

 E. Hannig. 2 My curiosity touching the matter, so far as this 

 plant is concerned, was aroused by Hannig's statement that the 

 mode of abscission, which is common only to Mirabilis and Oxy- 

 baphus, does not accord with any previously observed accounts, 

 and is made by him, therefore, to represent a new type, while his 

 figures appeared to me not to support his contention. It seemed 

 to me rather that a more exhaustive study of even the published 

 drawings of Loewi 3 and of Tison 4 alone would have led Hawk; 

 to see a strong resemblance between those and his own figures. 

 Before material of Mirabilis was available for my own obser- 

 vation, I ventured therefore to believe that he was not justified 5 

 in formulating a new type of abscission. Since then I have obtained 

 an abundance of material, and after a careful study of the process 

 in question in both stems and leaves, I find myself unable to alter 

 my opinion. 



1 Untersuchungen iiber das Abstossen von Bluten, etc. Zeitschr. Bot. 5:41 7- 

 3 Blattabldsung und venvandte Erscheinungen. Proc. Vienna Acad. 1:166-983. 



213] [Botanical Gazette, vol. 61 



