1894.] NATURAL SCIENCES OF PHILADELPHIA. 167 



this tissue would attempt to form shoots, many naturally being 

 crowded out, but enough finally making a growth to present a minia- 

 ture forest. The most remarka})le case of this nature came under 

 ray observation in 1893, and relates to two large Carolina Cotton- 

 woods, Populiis moniUfera, standing on the sidewalk at the corner 

 of Greene and Harvey Streets, German town. About the time of the 

 unfolding of the leaf, a hoi'se had gnawed away the bark, exposing 

 the wood for a space of nearly a foot in diameter. About midsum- 

 mer, when the new cambium layer Avas l)eing formed,' hundreds of 

 buds developing to leaves and branches, appeared from the edge of 

 the whole exposed surface of the new layer. It was a remarkable 

 sight that a layer of tissue, usually content to cover a wound with 

 new wood, should at the same time seem to be covered with scores of 

 what one would call seedling trees if they had been at the surface 

 of the earth. 



It must be well known to obsei'vers of trees which have had large 

 branches sawn off, that numerous buds producing branches will push 

 through the bark of the stump near where the upper portion was cut 

 away, proceeding, of course, from the primary raeristera tissue which 

 must have had the power to produce the necessary apical cells for 

 this bud formation. But it is not often that the same power can be 

 evidenced by similar growths from the exposed portions of wounds, 

 as the observations here recorded afford. 



The Fall of the Leaf in the Holly. 



Near Philadelphia the spring growth of the American Holly, 

 Ilex opaca, occurs in May. Simultaneously with the appearance of 

 the new growth the ground is strewed with fallen leaves. I have 

 thought, in common with most, if not all observers, that the swelling 

 of the new growth dislodged the old leaves, just as it seems to do in 

 the case of oak or beech leaves, where leaves that happen to remain 

 dry on the branches all winter, drop w^hen the new growth occurs in 

 spring. To my surprise I find that this is not the case in the holly. 

 After the copious fall already referred to, it is found that most of 

 the fallen leaves were those of last year. Two-year-old leaves on 



^I have shown in the Proceedings of the Academy, 1866, pp. 292-293, that it 

 is only aliout that time, in this tree, the tissue known as the cambium layer is 

 formed. 



