174 



by the shortening of alternate internodes, we must see in the stem 

 of the Catalpa which normally has decussating whorls of three 

 leaves, and in the maple twigs referred to, pairs of successive re- 

 duced internodes alternating with single normal internodes. Evi- 

 dence that this is the case is seen in an abnormal twig of Acer 

 Pennsylvanicimi, found by the writer, in which the leaves of one 

 pair were displaced, and so removed from each other, by a dis- 

 tance of Jg inch and those of the next pair by i|- inches. The 

 specimen is of further interest in the fact that the leaves of the 

 former pair were alsodis placed, but here laterally, so that they 

 lay in two separate axial planes, instead, as in the normal condi- 

 tion, in one. Such a displacement must occur in twigs which 

 normally bear paired leaves when a third appears in the whorl. 

 In the twig here described, however, the displacement was in the 

 wrong direction, when referred to the upper displaced leaf of the 

 next lower pair, so that three leaves were, in this way, crowded 

 upon one side of the twig. Had the other leaf, i. e., the lower of 

 the under pair, been the upper, the relation would have then been, 

 as one would have expected, regular. 



The use of Wings in the Fruit of Acer. — The generally accepted 

 view concerning the use of the wings in the fruit of Acer is that 

 they serve as organs of flight to aid in dissemination. It is not 

 impossible that they serve some other function, and I have en- 

 deavored to determine whether, during the development of the 

 embryo, they may be of use in manufacturing foods for its nu- 

 trition. A certain amount of anatomical evidence is present to 

 indicate that this is the case. Thus the venation appears to be 

 so disposed as to serve for the translocation of solutions toward 

 the embryo ; and the minute structure, both as regards the 

 stomata and the mesophyll, is very like that of a non-dorsiven- 

 tral leaf, such as that of Lactuca scariola, or the phyllodia of vari- 

 ous plants. There is but little development of spongy paren- 

 chyma ; otherwise the organ is quite leaf-like. 



By applying the iodine test it was shown that the wings are 

 very active in the making of starch during the day, and, as in 

 leaves, the materials accumulated during daylight suffered trans- 

 location. On the supposition that this movement of the starch 



