18 Prof. Hughes, On symmetry in Mulberry foliage. [Nov. 25, 



In seeking the explanation two facts have to be borne in mind. 

 First, that where the two masses meet at the miter their direction 

 of increment does not coincide. And secondly, that the growth 

 of the crystals is arrested along the margin by the ever-diminishing 

 surface upon which they are built up. 



(2) On symmetry in the foliage of a branch of Mulberry 

 with asymmetry in the individual leaves. By Professor T. McK. 

 Hughes, M.A., F.RS. 



The question of the forms of leaves has often been treated of, 

 but I do not know whether the particular point to which I now 

 call attention has been noticed. Looking at the mulberry trees in 

 the Fellows' Garden at Christ's College, I observed that young 

 branches thrown out from near the base of the trunk are apt to 

 bear scalloped leaves something like those of a vine. When in the 

 progress of the growth and development of the branch these 

 scalloped leaves are replaced by the normal forms, the change does 

 not take place by the gradual withdrawal of the lobes equally 

 all along the margin of the leaves, but the inside of the leaf, that 

 is the side next the branch, first returns to the undivided condi- 

 tion, while on the outside of the leaf the lobes are still conspicuous. 

 On one flat twig all the leaves were shaped like gloves, which 

 had a separate place for the thumb only, the other fingers being 

 inclosed together in a sort of bag. In this case the thumbs were 

 all turned outward, and the undivided margin was next the twig. 



Some apparent exceptions were found in which a leaf lobed on 

 the right was found projecting from the left side of a twig, or vice- 

 versa, but in all these cases, as far as I have been able to observe, 

 the leaf which appears not to conform to the rule is growing from 

 a small offshoot of the twig, so that a leaf which is left-handed in 

 form with reference to the principal twig to which it at first seems 

 to be attached, is right-handed with reference to the subordinate 

 twig from which it really grows. 



It would thus appear that the symmetry which has been lost 

 in the individual leaves still exists in the branches, so that the 

 twig with all its leaves may be regarded from this point of view as 

 one large leaf lobed on its margin, and therefore only the outside 

 margin of each individual leaf partakes of this scalloping, that is, 

 the left side of those on the left of the twig, and the right side of 

 those on the right of the twig. 



