186 PROCEEDINGS OF THE ACADEMY OF [1897. 



In another part of my grounds I had about one thousand two 

 year old plants, transplanted the previous spring when one year old. 

 Interested in learning how long the opposite leaved individuals — 

 for I assumed there must have been many of that character — would 

 continue of that class, I found that all but nine had started on the 

 opposite leaved plan from the commencement of the second season's 

 or last spring's growth. These nine continued to form opposite 

 leaves on all the leading branches, but the secondaries which pushed 

 out from the primaries during the summer, had alternate leaves. 

 One may say that by the third year all trace of the opposite leaved 

 system will disappear. 



It has been assumed in phyllotaxy that the underlying law in 

 leaf-arrangement is to provide for the very best exposure to the 

 light of the foliar organs. That leaves must have light, and that 

 leaf-arrangement must surely have some reference to this fact, needs 

 no argument to support it. But it must be obvious to an experi- 

 enced observer that leaves are very far from being always arranged 

 in the best manner t» this end. One need never go far for an 

 illustration that if advantageous exposure to light be all that is in- 

 volved, the plan could be vastly improved. There has always 

 seemed to me fair ground for believing there must be a deeper un- 

 discovered law, and I have been continually on the watch, without 

 much success, for clues to this deeper mystery. 



In the case of these elms, the pairs of leaves are decussate, 

 every other pair being exactly superposed with those beneath. 

 Such an arrangement would not be thought the most favorable for 

 the action of light. On the other hand, the alternate distichous ar- 

 rangement in these young plants, and measurably in the older ones, 

 causes the leaves in many cases to have the leaf-blade vertical, or, 

 where the nodes are not particularly distant, to have portions of the 

 leaf-blade overlapping another leaf, in effect reducing considerably 

 the available leaf surface. 



One point of special interest is that the nine trees which carried 

 over the opposite leaved arrangement through the second year are 

 much weaker in growth than the others. I think I might safely say 

 that superior vigor of growth and the alternate arrangement of the 

 leaves are correlative. 



SPECIAL FEATURES IN A STUDY OF CORNUS STOLONIFERA MX. 



Some interesting features for biological study are furnished by 

 Coraus stolonifera of Michaux, Comas alba, or the " white-berried " 

 Dogwood of many authors. 



