394 Farmer and Hill. — Arrangement and Structure 
rest of the tissues that lie outside of it, and are regarded as 
forming no integral part of it. 
The endodermis is a tisslie, oh the importance of which 
great stress is often laid, perhaps oh account of its obvious 
characters (when present) and perhaps also because we possess 
so very little knowledge as to its physiological significance. 
And yet this same endodermis is almost whimsical in the 
vagaries it exhibits both in respect of its non-appearance in 
places where it (theoretically) should be present, as well as 
in its frequent occurrence in anomalous situations. 
Strasburger indeed, with the acuteness that always marks 
his treatment of intricate problefns, clearly recognized the 
difficulty, and he frankly abandoned the endodermis as a 
delimiting zone of prime morphological importance. He, as 
is well known, proposed the term Phloeoterma to signify the 
band of tissue immediately lining the stele, and peripherally 
separating it from the cortex ; and the existence of this 
phloeoterma is to be conceded, even when it cannot be objec- 
tively distinguished by special markings on its cell walls. 
But the special advantages of the term would really appear 
to be involved in a tacit assumption of its coincidence, or 
analogy, with the older form of demarcation as laid down by 
Hanstein. The latter writer, at least by implication, went 
farther back than the differentiating tissues to the meristems 
from which they took their origin. So long as ‘ monostely ’ 
alone is concerned the phloeoterma may serve, but in cases 
of polystely and schizostely, where it might be of critical 
value, it seems to possess but little advantage over the endo- 
dermis itself. For to put one of several aspects of the case, 
why should the entire limiting layer of Vascular strands con- 
taining i+n bundles be regarded as a phloeoterma, whereas 
if there be but i bundle in the strand, part must be regarded 
as phloeoterma and the rest as endodermis ? What is the 
special value of the addition of n bundles, that it should so 
alter the conception as to the ‘ morphological * nature of the 
sheath? But the confusion becomes incomparably more pro- 
found when the vascular continuity of the main cylinder or 
