1206 Notes . 
and II); in the former instance the, excretion is apparently able to pass through the 
cell-walls, as in the case of Datura} 
Although these sugary excretions are to be regarded primarily as of the nature 
of waste products, nevertheless they may have a subsidiary function to perform in 
attracting insects whose presence may be of benefit to the plant. 
The varied instances of ‘ Myrmecophily ’ have been ably expounded by different 
authors, and Ridley 2 has alluded to Platycerium biforme in this respect. Its ‘ man 4 ^ 
leaves', with their concomitant of debris, constitute an ideal home for ants in )heir 
native habitat, and these sugary excretions, presuming they occur in nature, 
only regard as an adjunct to an interesting case of mutualism. 
R. DUMMER. 
Royal Botanic Gardens, 
Kew. 
1 Strassburger, Textbook, Engl. Trans., p. 191, 1903. 
3 Ann. Bot., vol. xxiv, 469, 1910. 
CORRECTION BY PROFESSOR BOWER.—There is a sentence in my 
paper ‘ On Medullation in the Pteridophyta ’ which I desire to amend. It is on 
p. 573, line 17 of the present volume, and it runs as follows‘ The fact of soleno- 
stelic structure in such a Fern as Pteris aquilina can have no direct bearing upon 
questions of their medullation, &c/—that is, the medullation of seed plants. This 
sentence as it stands may be a stumbling-block to purists in description. It will 
better stand thus‘ The fact that solenostelic structure exists in the Pterideae, and 
that a modified derivative of that structure is seen in Pteris aquilina , &c.’ The 
argument is unaffected by the change. What is intended is to show that such a type 
as Pteris aquilina , or indeed any of the Pterideae, can be no guide directly to the 
phyletic origin of the structure seen in seed plants unless it can be shown that the 
Pterideae had a common ancestry with the seed plants compared, and that that 
ancestry was already medullated and solenostelic before the two phyla were 
segregated. Without such evidence, comparison can bring to light nothing more 
than distant analogies of structure. It is obvious that the argument remains the same 
whether the Pterideae are quoted as a whole, or a specific case, such as Pteris 
aquilina. 
It may be added that phyletically the Pterideae are not a very primitive type of 
Ferns, while in anatomical as well as in certain other characters Pteris aquilina is 
itself an advanced representative of the family. 
Glasgow, 
August , 1911. 
