Vascular System of Matonia pectinata. 509 
rhizomes of relatively starved plants can leave no doubt whatever of the 
correctness of this view. Indeed, no more complete illustration of Gwynne- 
Vaughan’s hypothesis could be given than that afforded by the origin of the 
first internal accessory cylinder from the original stele. Of the two alternative 
suggested methods, however, by which a solid internal strand might be 
converted into a closed hollow cylinder (the enlarging, curving round and 
meeting of the edges, or the branching and subsequent fusing of the branches 
into a cylinder 4 ), neither will hold for Matonia . 
In the case of all three cylinders, i. e. the original stele, and the two 
internal accessory cylinders, the solenostelic structure is arrived at by 
means of the development first of internal phloem within the xylem, then 
of internal endodermis within this phloem, and finally of internal ‘ extra- 
stelar ’ parenchyma or pith within this endodermis. In other words, the 
cylinders pass through the Lindsaya-stage on their way from protostelic to 
solenostelic structure. 
The appearance of the Lindsay a- phase in the ‘ontogeny’ of all three 
cylinders of Matonia adds another to the growing series of cases in which 
this type precedes the solenostele in the development of the individual 
Fern-stem 2 , and serves to strengthen the hypothesis we put forward in 
a previous note 3 , that the Lindsay a - type is also the phylogenetic precursor 
of the solenostele. This hypothesis has been strongly supported by Gwynne- 
Vaughan, who has brought forward much new evidence in its favour 4 , and 
we have now little doubt that it may be taken as of general application. 
There is such a strong prima facie case for holding that the stages of 
vascular structure met with in passing up the stem of a Fern which has 
attained a certain degree of complication represent, in a general way, the 
phylogenetic stages through which the adult stem has passed in arriving 
at its present structure, that we need have no hesitation in interpreting the 
one in the light of the other, but we must remember that it does not follow 
that this parallelism will be complete in all its details. In the present 
case, for instance, the local internal thickening of the xylem in the region 
of the leaf-gap, which is the precursor of the formation of internal cylinders, 
appears at an extremely early stage in the third node of the youngest plant 
we found, when the leaf-trace consists of a very slightly curved arc of 
tissue. At a very slightly more advanced stage the internal ridge of 
xylem actually becomes free from the external, and runs for some distance 
isolated in the internal phloem. The beginning of the formation of an 
internal endodermis is seen at an even earlier stage. Whatever may be 
1 G wynne- Vaughan (’ 03 ), p. 704. 
2 According to Chandler (New Phytologist, vol. iii, p. 123), the Lindsay avstage is general, 
preceding the solenostelic stage, in the bases of the young stems of many species of Ferns he has 
investigated, mostly dictyostelic forms. This is quite borne out by Chandler’s full paper in the last 
issue of this journal (Ann. of Bot., xix, p. 365). 
3 Tansley and Lulham (’ 02 ). 
4 G wynne- Vaughan (’ 03 ). 
