18 The Nature and Origin of Stipules. 



Coloiul}, C — Recherches sur les stipules. Ann. Sci. Nat. (VII), 6 : 1- 

 76. 1887. 



This paper is the result of an exhaustive anatomical study of 

 stipules and their homologues. The results obtained are of great 

 interest and value. The}- are admirablj- summed up at the close 

 of the paper as follows : 



" When a leaf is sheathing, the sheath may be prolonged in a 

 ligule situated above the point of insertion of the blade upon the 

 sheath. 



" In this organ three regions may be recognized : 



" 1. The lateral regions into which the marginal bundles of the 

 sheath are merely prolonged. These regions naturally do not exist 

 if all the bundles of the sheath enter into the leaf, 



" 2. The stipular regions, the bundles of which arise from a 

 doubling of the last bundle of the sheath entering into the leaf. 



" 3. The axillai-y region, which unites the two stipular regions, a 

 lamina, usually of parench^-ma, but which may receive bundles 

 arising: from the internal doubling of those bundles of the sheath 

 which become petiolar. 



" The sheath may be reduced even to complete disappearance 

 without a consequent disappearance of the ligule. 



" 1. If the ligule is complete with its three regions, I give it 

 the name of an axillary ligule. 



" 2. If the stipular and axillary regions onl}- persist, the sheath- 

 ing regions having disappeared, we have an axillar}- stipule. 



" 3. If finally the axillary region divides into two halves, right 

 and left (which would not be remarkable, considering its purely- 

 parench3matous nature), the stipular regions exist alone at the 

 base of the petiole, and we have then stipules properly so-called. 



" Stipules and the ligule are then organs of the same nature, 

 between which it is possible to find all forms of intergradation, 

 the stipule being a portion of the axillary ligule. 



" When, finally, the manner of origin of the bundles of the 

 stipule is studied, we arrive at the following definition of the organ: 

 An appendage inserted on the stem, at the base of the leaf, all the 

 bundles of which arise exclusively^ from the corresponding foliar 

 bundles." 



Each of the tendrils of a leaf of Smilax is characterized as a 

 demi-ligule, the " stipule " of Potamogeton as a ligule identical with 

 that of grasses, the ochrea of Polygonum and Platanus as axillary 



