1893.] NATURAL SCIENCES OF PHILADELPHIA. 299 



edges of the leaves are ciliate. The stems are bifariously hirsute. 

 No explanation of this seems to the author reasonable but that 

 this results from the meeting of the cilia on the edges of the narrow 

 bases of the foliar organs, and which, at the node above, expanded 

 into a laminal condition — a leaf blade. 



Branching of Euphorbia hypericifolia and E. maculata. 



There are some peculiarities in the branching of these two species 

 of Euphorbia difficult of explanation in each case, but very clear 

 when studied in comparison with each other. As a general princi- 

 ple in plants we look for an axillary bud at the base of every leaf, 

 or we can usually conceive some reason why the axillary bud has 

 not been develoj)ed. Taking a branch of Euphorbia hypericifolia 

 we find the leaves opposite, but one somewhat stronger than the 

 other. The main stems are somewhat flexuose. On the one side of 

 the main shoot an axillary bud has developed from the base of the 

 leaf into a weak lateral branch, but there seems to be no trace of 

 an axillary bud at the base of the leaf opposite. We ask, what has 

 become of the bud which should have been at the base of that leaf? 



In E. maculata the branches are not flexuose. A straight stem 

 proceeds from the main branch, having many pairs of leaves at the 

 nodes. At the base of one of the leaves there is an axillary bud, 

 no bud at the base of the leaf opposite, which seems very closely 

 attached to the straight central axis or main stem. 



Returning to E. hypericifolia we find, toward the end of the sea- 

 son's branch, a very weak peduncle between the forks of the 

 branches, having at the apex a head of flowers. We now see that 

 this pedicel was the original main stem, and that what we have 

 before taken for main stems were the jiroducts of axillary buds in 

 cases where the main axes were wholly suppressed. With this total 

 suppression came the effort on the part of one of the axillary 

 branches to supply the loss, and this is the one which has given the 

 impression that the subtending leaf had no axillary bud. There 

 was a bud, and that bud pushed so strongly as to become a substi- 

 tute for the suppressed central stem. The weaker bud, axillary to 

 the weaker leaf, either continues as a bud or pushes into a weaker 

 axillary growth. It is, however, of sufficient strength to compete 

 somewhat with the opposite stem growth, which cannot, therefore, 

 become perfectly straight, and the result is, as we see, a necessarily 

 flexuose habit. . 



