Q 



16 



On the Bract in Tilia- 



The small leaf adherent for some half its length to the com- 

 mon peduncle in the Linden tree, is known as a wing-bract. I 

 do not know that any purpose has been suggested for this bract, 

 except for aiding in the distribution of the seeds. In the Hun- 

 garian Silver Linden, Tilia petiolaris (not probably distinct from 

 T. arge7itca) Avhich I have had the opportunity to examine closely 

 this season, they evidently possess a lifting power which must 

 have had some ofifice of usefulness connected with it. The com- 

 mon peduncle Itself is comparatively weak, and only for the 

 attachment to the leaflet would hang loosely from the axis. 

 But the leaflet being greenish, and with the usual power of 

 a green leaf, turns up toward the Hght, and draws up with it the 

 common peduncle, so far as the attachment thereto. From that 

 point the peduncle curves downward. In this way the cymes 

 are kept much wider apart than they would be if each dropped 

 loosely from the axil, where they would be in each other's way. 



The leaves of Lindens are arranged in horizontal lines on each 

 side of the branch. This does not seem to be advantageous if 

 the purpose of the various methods in phyllotaxy be to secure to 

 the leaves the most light. In this species of Linden the leaves 

 are comparatively large, and the nodes comparatively close, so 

 that a large portion of one leaf is overlapped by another, as in 

 shingles or thatch on a roof In rainy weather they act as shelter 

 tents to the flowers beneath. The cyme is lifted up right under 

 the leaf by the upw^ardly curving power already noted. During 

 an incessant rain storm of two days' duration, I found the flowers 

 securely protected from the rain by this arrangement. 



For the whole of this time the honey-bees in great numbers 

 from hives some i,ooo feet away, were incessantly at work. I 

 do not remember observing bees at work in rainy weather as 

 these were working here. If the Lindens had been purposely, 

 adapted to find a wet- day job for the bees, the arrangement 

 could not have been any more perfect. It is difficult to un- 

 derstand how such adaptation could have been evolved from 

 the standpoint of an y especial use to the plant itself. Nor is it 



*Read before the meeting of the Botanical Club of the A. A. A. S.. at Cleve- 

 land, Aug. 20th, iS88. 



