164 
Notes . 
phloem of the inferior and superior nodal islands continued respec- 
tively through the lower and the upper internodes till they meet 
corresponding extensions from the next nodes below and above, it 
is clear that we have reached the Lindsay a-type, and have obtained 
an internal stelar phloem-system forming a satisfactory attachment for 
the internal phloem of the meristele, which has now become completely 
concentric. 
Finally, with regard to the change from the Lindsaya- type to that 
of the solenostele, we have the strand of parenchyma or sclerenchyma 
surrounded by its own endodermis in the concavity of the meristele, 
already usually carried down into the ‘ inferior phloem island 1 in 
Gleichenia , and into the ‘ inferior phloem-bay ’ in Lindsaya (Fig. 10). 
We have only to imagine it continued down in the centre of the 
internal phloem, till it reaches the next node, and the change is made. 
In Davallia ( Microlepia ) pinnata we have found this change apparently 
in progress. Immediately above the node the stele has the Lindsaya- 
type with internal phloem alone, but a stout strand of sclerenchyma 
continuous with that lying in the concavity of the horse-shoe-shaped 
open meristele, and surrounded by an endodermis, penetrates the 
internal phloem of the stele, ending blindly some little distance above 
the next node below (Fig. 17). The appearance presented corre- 
sponds strikingly with Boodle’s Fig. 17, which we have reproduced 
as Fig. 16, of the node of Gleichenia dichotoma } representing 
a section taken just below the separation of the xylem of the 
leaf-trace. 
The above is a very brief indication of our ideas as to the probable 
phylogenetic meaning of the new facts. In this preliminary note they 
are necessarily expressed imperfectly and somewhat dogmatically. 
Detailed qualification would be out of place, but we may perhaps 
point out that we do not intend to convey the impression that in our 
opinion the method we have roughly sketched is necessarily the only 
way in which the solenostele has arisen in evolution. Doubtless in 
some cases the pith may have come before the internal phloem, and in 
such a case the stage represented by the Lindsaya- type would not be 
passed through at all. 
A. G. TANSLEY. 
R. B. LULHAM. 
University College, London. 
February , 1902. 
