Unusual Stipules of Acer Nigrum Michx. 259 



UNUSUAL STIPULES OF ACER NIGRUM MICHX. 



Flora Anderson, Indiana University. 



In the autumn of 1921 when the leaves began to fall, some leaves 

 of Acer nigmm were noticed that had very prominent stipules. The 

 tree from which these leaves came is just north of Biology Hall on 

 the Indiana University Campus. Since it is 45 to 50 feet to the first 

 limb, no leaves were studied while on the tree. By examining the 

 fallen leaves one could find almost all variations, from those having 

 no noticeable stipules to those having very prominent aecidulated stipules 

 on long slender stalks. The place of attachment of the stipules varied 

 from the base of the petiole to the base of the blade (figs. 4 to 9). The 

 blade of the stipule was either straight or aecidulated. Figures .3 and 

 4 show both types on the same leaf. 



Britton^ in his description of Acer nignim says . . ; "the leaf- 

 stalks are also hairy, at least when young, and are expanded at the 

 base, often bearing stipules which are sometimes 3 or 4 cm. long". On 

 a single tree one may find leaves with the petioles scarcely expanded 

 at the base, and other leaves with very large, conspicuous stipules — the 

 blade of the stipule sometimes 6 or 7 cm. long — on slender stalks 

 (fig. 13). Then there may be found all gradations between these. 

 Hough" says . . ; "petioles stout and generally bearing stipules 

 at the enlarged base". He figures a branch and calls attention to "the 

 presence of a few small stipules. They are occasionally much larger". 

 Deam^ in his description of the species says . . . "petioles usually 

 3-15 cm. long which are more or less swollen at the base and by 

 maturity develop a scale-like appendage on each side of the petiole at 

 the base — especially on each of the terminal pair of leaves, sometimes 

 with foliar stipules which are 2-3 cm. long on stalks of equal length". 

 His plate 114 is a photograph of a branch of Acer nignim which shows 

 two leaves with unusual stipules — one at the base of the petiole, the 

 other near the blade of the leaf. Gray* mentions; "stipules often con- 

 'spicuous" and again', "Stipules large, early deciduous." Quite a number 

 of authors make no mention of stipules in their description of Acer 

 nigrum. 



Since the taxonomist had made no special note of these unusual 

 stipules, the writer thought they might be "early deciduous", and in 

 the spring of 1922 began to examine Acer nigriim trees for leaves with 

 stipules of unusual character. During the spring and summer, trees 

 on the Indiana University Campus and on the streets of Bloomington 

 were observed. On almost all of these trees were found leaves of different 

 types, varying from those with practically no stipules to those with large 

 foliar aecidulated stipules on slender stalks. The point of attachment of 



' Britton, Nathaniel Lord. North American Trees, p. 651. 1908. 

 - Hough, Komeyn Beck. Handbook of the Trees of the Northern United States and 

 Cftr.iida. pp. ;-!26-327. Fig. 382. 1907. 



= Deam, Chas. C. Trees of Indiana, p. 246. pL 114. 1921. 



■> Gray, Asa. New Manual of Botany. 7th Ed. p. 558. 1908. 



^ Gray. Asa. Field, Forest and Garden Botany. Revised, p. 112. 1895. 



"Proc. 38th Meeting, 1922 (1923)." 



