Igor] ANATOMY OF THE OSMUNDACEAE 409 
leaves. Potonié also explains the origin of his second primitive 
type the ‘pericaulom,” the homologue of the siphonostele, on 
mechanical grounds. 
In the light of these theories we can now apply ourselves to 
an interpretation of the anatomy of the vascular system of the 
Osmundaceae, and likewise note if the facts already dealt with 
throw any light on the theories. 
First, we are in a better position now to decide whether the 
internal endodermis of O. cinnamomea is phloeotermal or not. 
It has been noted that in similar cases, that is, in gamodesmic 
stems, Strasburger has denied the phloeotermal character of the 
internal endodermis. With regard to the internal endodermis 
the following facts have been observed: 
I. There is present the characteristic cuticularized ‘“ radial 
dot.”’ 
2. The structure and contents of the cells are materially the 
Same as of the external endodermis. 
3. The sheath is continued into the portions which in some 
individuals present the phenomenon of internal phloem, just as 
in any form called by Van Tieghem and Strasburger gamostelic. 
In the gamostelic type the phloeotermal character of the internal 
€ndodermis has been admitted. 
4. It generally connects with the external endodermis through 
ramular gaps, and by no means rarely through foliar gaps. 
When this occurs, there is no point at which it could be said that 
the one stops or the other begins. 
Having verified these facts in a great many cases, lam there- 
fore of the Opinion that the internal and the external endodermis 
are homologous tissues. 
Second, are the medullary tissues morphologically equivalent 
to the cortical ? Again we recapitulate observations. 
1. They do not differ in structure or in contents. 
2. The medulla very often contains brown sclerenchyma, at 
least in three species studied, a tissue which, in other ferns, 
never constitutes a part of the stele. 
3. Medulla and cortex connect more frequently than not 
