28s BOTANICAL GAZETTE. 



twin petiolar glands of various species of Priinus, which are known 

 to be marginal outgrowtlis, representing the tendency to division 

 which has produced the compound leaves of other Rosaccce, it was at 

 once inferred that the glands of /'("//////y are of a similar nature; hut 

 since the Salicaceie have simple leaves, analogy failed, and actual 

 demonstration was apparently no verv easy matter. An examination 

 of other species, though at first yielding no satisfaction, finally snlved 

 the problem by affording several series of abnormal cases (Figs 1-5), 

 in which the marginal nature of the glands was clearly shown. Thus, 

 in a cultivated plant of P. trcniula, var. pendiila, the glands were 

 found to be usually four in number and quite distinct, the outer pair 

 rising on long stalks, the (Others being more nearly sessile (Fig. i); 

 but in one case (Fig. 2), instead of these there were several sessile 

 glands, gradually diminishing in size, arranged along the margin of 

 the leaf-blade — which, it should be added, is distinguishable in most of 

 the species as a double ridge running dcwn the top of the petiole. 

 The paired glands of P. balsaiiiifcni, var. candicans are also quite 

 frequently displaced, so as to terminate rather co.-irse marginal serra- 

 tions; and illustrative cases were found in P. i/ioiiili/era (Figs. 3 and 4), 

 P. ciliata, P. Sieboldii, P. suavcolens, and P. trichocarpa, in the Gray 

 herbarium at Cimbridge. Finally small serration glands of the usual 

 type grading into the [)eti()lar glands, being found in P. treimila, var. 

 pendula, P. trichocaipa (Fig. 5) and other species, left no doubt of the 

 homoloay of the members in question with those oi Priuuis^ RiciJius, 

 etc., and their origin is in no wise different from that of the smiilar out- 

 growths found on the leaves of certain willows. 



Observation showed that they do not occur on all of the leaves, 

 but, as a rule, only on the first half dozen or less, which appear on 

 each branch in the early spring; and in summer and autumn, these hav- 

 ing fallen, it is sometimes possible to examine several branches with- 

 out detecting a single glanduliferous leaf, on species which produce 

 them abundantly earlier in the season. 



With a view to ascertaining their prevalence through the genus, I 

 examined such species as were found living; and, an opportunity 

 offering, those represented in the herbarium of Dr. Gray, with the 

 following results: In the typical P. bahamifcra two separate glands 

 were found at the b.ise of the blade, and the serrations oi the latter 

 commonly ended in smaller, otherwise similar organs; and in the var. 

 r(7?/,^/rff;7j- the basal glands were always present, though those of the. 

 teeth were not so frequent. Those of P. ciliata were quite similar. 

 On the broad leaves of P. EiipJiratka two small but we 1 developed 

 glands were found, but none were seen on the narrow leaves of the 

 same species. P. grandidentata and P. heterophyUa have well developed 

 petiolar glands, and the latter has an abundance of serration glands. On 

 P. monilifcm and P. anguiata the basal glands are present, and often 

 stalked and divided (Fig. 3); in the larger leaves they are frequently 

 of large size. \\\ P. pniinosa \\\Qy are large and prominent; '\w P. 

 A7^/!'6'/i// they are present and frequently remind one of those in P. 

 candicans. In P. suaveolens they are large, and clearly belong to the leaf- 



