62 PROCEEDINGS OF THE ACADEMY OF [1889. 



On the nature and office of Stipules. The author has printed a 

 paper in the Proceedings of the Academy, 1870, pp. 114-117, on the 

 Stipules of Magnolia, showing that the stipules not only performed 

 the office of bud-scales, but that the petals were transformed stipules, 

 and not metamorphosed leaves as we usually understand them to be. 

 The good friend whose loss we all deplore, Prof. Asa Gray, gen- 

 erously examined the manuscript before publication, and expressed 

 himself much pleased with the deductions drawn, observing, how- 

 ever, that if his memory served him right some German observer 

 had before suggested that petals are occasionally but modified stipu- 

 les. This is so obvious, that it would be surprising if the matter 

 had not been discussed somewhere, but the author has never been 

 able to discover the treatise that Professor Asa Gray believed he 

 had read on the subject. It is safe to say that, as a general rule, 

 stipules are not regarded as of any material importance in the 

 economy of plant life. In the treatment of this subject they are 

 simply spoken of as " appendages to the leaves," referred to as oc- 

 casionally serving as a bud-scale, and then dismissed from considera- 

 tion. 



There is no essential difference between a stipule and the dilated 

 base of a petiole. In some natural orders the presence of stipules 

 characterizes every genus ; in allied orders the complete stipule may 

 be wanting, but the bases of the leaves are widened and become thin. 

 The leaves are then characterized as having petioles dilated at the 

 base. 



It is worthy of remark that in plants having dilated petioles the 

 leaves with the petioles so dilated have much shorter petioles than 

 those on the same plant not dilated ; in Ranunculaceae and Umbel- 

 liferre for instance. The same rule obtains in those genera where 

 there is a difference in the size of the stipules in the same plant — 

 some Rosacea}. The size of the stipules is in inverse proportion to 

 the length of the petioles. It is important to note that elongation 

 is in a measure suppressed in proportion to the development of the 

 stipule or the dilated petiolar base. This may be seen in the case 

 of Corydalis fiavula (see Contributions IV, page 58). It may 

 also be noted in an examination of a stalk of clover, or a flowering 

 branch of the rose. The stipules become larger and the petioles 

 shorter as the flower bud is reached. 



Exactly the same order follows the production of bud-scales, when 

 a branch is about finishing its season's growth. Towards the end 



