410 Boodle . — Anatomy of the Schizaeaceae. 
suppression of the leaves on the lower side of the creeping 
rhizome, which at any rate appears probable, the parenchyma- 
tous tissue representing the original leaf-gaps on the lower side 
appears to have been converted into vascular tissue, and the 
leaf-gaps thus repaired. This would agree with the view that 
the leaf-gap-parenchyma is really stelar tissue in the phyloge- 
netic sense. Again, A. aurita , if its structure were better known, 
would form an interesting type for comparison with A. mexicana . 
What has been said above may at any rate show that 
a fuller investigation of species of Anemia would probably 
throw a great deal of light on questions connected with the 
morphology of the stele. 
A few more remarks must be made with regard to the 
seedling. There is probably a tendency for plants to show 
acquired structural characters at earlier and earlier stages in 
their ontogeny. The strip of endodermis (el) seen in Fig. 28 
is apparently useless, and may represent an attempt to form 
a loop of endodermis such as is found at a later leaf-gap 
(Fig. 31), and for which in the small stele there is not 
sufficient room. The early connexion between inner and 
outer phloem and between other tissues in the seedling 
suggests a possibility, though this is very hypothetical, that 
when a new kind of tissue is to be formed, e. g. internal phloem 
from stelar parenchyma, contact with similar tissue, in this 
case phloem, may be necessary. That is to say, protoplasmic 
continuity between different elements when young may in 
some way help in leading to the formation of corresponding 
mature elements ; or one might say a ‘ contagion ’ for forming 
a special kind of element is handed on. 
To conclude the subject, the homologies of different types 
of stelar structure at present appear doubtful, but the writer 
inclines to the view that the medullated, solenostelic, and 
dialystelic types have been derived from the solid stele by the 
transformation of its central tissues into parenchyma in the 
first case, and into parenchyma together with a certain amount 
of phloem and endodermis in the second and third cases. 
The time for the application of rigorous terminology does 
