Boodle . — Anatomy of the Schizaeaceae. 405 
out by Strasburger (’ 91 , p. 441). On account of his view of 
the different morphological nature of the endodermis in 
different cases, Strasburger used the term 4 endodermis ’ in 
the physiological sense, for the layer bearing cuticularized 
bands, and introduced the term ‘ phloeoterma 5 to designate 
the innermost layer of the cortex (’ 91 , p. 435) ; but he used 
the term phloeoterma in a way that may be called in question 
in the case of polystelic Ferns. As the morphological value 
of the endodermis cannot be said to have been definitely 
established in the case of 4 polystelic ’ plants, it would be 
preferable to call the cutinized layer in them an endodermis, 
and not to apply the term phloeoterma to it, as Jeffrey and 
Gwynne- Vaughan have done, until it has been if possible 
proved that this layer is the innermost layer of the cortex. 
In Jeffrey’s work the endodermis is regarded as revealing the 
position of the limit of the cortex, and is called phloeoterma ; 
and the continuity of tissues in the seedling is relied on for 
determining their morphological nature. 
The latter point is shown by the following statement 
regarding Ranunculus In the young axis the stelar system 
possesses an internal phloeoterma, which is continuous with 
the external phloeoterma through the foliar gaps, and is 
therefore of the same morphological value.’ This conclusion 
cannot be said to carry conviction. It is not wished in any 
way to imply the impossibility of such interpretations being 
correct, but simply to point out that proof is required as to 
the morphological nature of the endodermis, and as to the 
value of the continuity of tissues. 
In relation to the questions involved it will be as well to 
attempt to regard some of the structures from a physiological 
standpoint. The function of the endodermis appears to be to 
form a closed layer of cells shutting off vascular tissue from 
tissues which contain intercellular spaces (Strasburger, ’ 91 , 
p. 611), and thus to prevent air from penetrating to the 
tracheae. The mechanical firmness which enables the endo- 
dermis to escape rupture of its cells is attained by the network 
formed by the tangential suberized bands (Haberlandt, ’ 84 , 
