142 
The Stelar Theory. 
cortex and cylinder is much more generally pronounced than in the last 
class; the author cites seven plants only in which the limit by means 
of an endodermis is obscure. Owing to the agreement in general 
structure between the stems of Gymnosperms and Dicotyledons it 
follows that cortex and central cylinder are respectively homologous 
parts in each. The same must also hold good for Monocotyledons, 
for Von Mohl has shewn, from a study of stelar development in 
Palms, that the scattered arrangement in these is founded on the 
same basal plan as the hollow cylinder of Dicotyledons. 
Under this section of the book is brought the “Comparative 
Anatomy of the Young Plant” (of which chapter 4 treats), for the 
reason that the author considers “development” or “ontogeny” as 
being concerned with the differentiation of the varioustissues from the 
meristem; and that in studying the development of the young plant 
we are concerned with that branch of comparative anatomy which 
compares together, not different plants, but the different parts 
of one and the same plant. It is a special division of the subject 
concerned with the study of fully-formed , yet early-developed organs. 
The various English and American authors who are identified with 
this method of investigation are noted and Van Tieghem’s theories 
shortly discussed, the conclusion arrived at with regard to this latter 
author being that, although in some points, especially with regard 
to the subjects of polystely and astely, a revision of his views is 
desirable, yet the results of the researches of the various authors 
mentioned constitute an excellent confirmation of his main position 
that the monostelic is the primary structure in all vascular plants. 
Finally, in the last chapter “General Considerations and Con¬ 
clusions,” the wide sweep of vision and enlightened ideas of the 
author shine forth. We are here again forcibly reminded, and at 
greater length, of the comparative worthlessness of developmental 
data in determining the morphology of the various tissues, and are 
rather directed to the comparative method as the only reliable agency 
for this end ; both Van Tieghem and Strasburger being quoted in 
support of this position. Interjected in the midst of the chapter, in 
a footnote, appears a glossary of all the terms adopted by the 
various authors in connection with the stelar theory. Considerable 
attention i<? devoted to the position assumed by Jeffrey, in opposition 
to Van Tieghem, that the pith belongs, not to the stele, but rather 
to the cortex, as shewn by the presence of an “ inner endodermis,” 
the continuity of pith and cortex through the leaf-gaps, and the 
absence of a pith in many stems of seedling plants. The same idea 
is held by Faull and by Farmer and Hill. It is with able lance 
that our author enters the lists of discussion on the burning 
questions connected with stelar morphology. In the first place he 
considers that Jeffrey, in common also with Van Tieghem, 
Strasburger, and Gwynne-Vaughan, labours under a fundamental 
fallacy in regarding the ontogenetic continuity of any two tissues 
as affording the criterion of their homology. One author only, viz., 
Boodle (whom he quotes) has had the insight to see otherwise. No! 
“if cortex and pith,” says our author, “ were homologous, this would 
mean that the tissue which, in the ancestors of the plants concerned, 
constituted the cortex, reappears in their modern representatives 
partly as cortex and partly as pith. The cortex must, therefore, in 
the course of the phylogenetic development have become intruded 
