210 PROCEEDINGS OF THE ACADEMY OP 



June 22. 

 The President, Dr. Ruschenberger, in the chair. 

 Twent} r -three members present. 



The Relation of Light to Stomata. Mr. Thomas Meehan exhi- 

 bited a leaf taken from a small tree of Acer pseudo-platanus the 

 common sycamore maple which had assumed an inverted posi- 

 tion. The tree was three years old from seed, and all the leaves 

 were of that character. The young leaves first appeared in their 

 normal condition, but as the petiole lengthened, the leaf blade 

 bent under, so that the under surface was exposed to the full sun- 

 light, and under the petiole above. He also exhibited a young 

 oak from an acorn sown in the spring, and which he believed to be 

 Quercus Catesbeei, and in which all the leaves were vertical, and 

 not with their surfaces on a plane witli the horizon, as is the case 

 with all other seedling oaks and American trees. He said it was 

 possible this position of the leaves was not continued with the 

 increased age of the tree, or it would have been observed and 

 placed on record. Of several hundred young plants all had the 

 same character. 



The facts were simple in themselves, but had great interest to 

 the student in vegetable physiology. The stomata were usually 

 on the under side of the leaf, and believed to be there of a neces- 

 sity. Our leading botanical text book taught that stomata were 

 breathing pores, and could not carry on their essential operations 

 when exposed to direct sunlight; and the same high authority had 

 suggested that if leaves of this character could be inverted, and 

 forced to remain in this condition, the plant would inevitably die. 

 The maple did not die, but had been during all its existence as 

 health}- as others of the same species growing near it. A large 

 number of the proteaceous and nryrtaceous plants of South Africa 

 and Australia, and of which the now famous Eucalyptus globulus 

 is a familiar example, had their leaves vertical, as in this oak. 

 This had been accounted for by the statement that these leaves 

 had stomata on both surfaces of the leaf, and the effort of these 

 stomata to face the earth had of course resulted in an even bal- 

 ance of power, in which neither side had any advantage. The 

 stomata on each side of the leaf had to face the horizon. Suppos- 

 ing this might account for the position of these oak leaves, they, 

 as well as the maple, had been examined microscopically by Dr. 

 Hunt, of the Academy, and found to have stomata only on one 

 the normal side. He thought it safe to conclude from these facts, 

 that the accepted theories of the relation of stomata to light re- 

 quired some modification. 



