tn the f Seedlings ’ of Certain L eptosporangiate Ferns . 375 
trace becomes more advanced this endodermal layer disappears, and 
the mature leaf-trace at this stage consists of two vascular strands sur- 
rounded by a common endodermis. The further processes involved in 
the exit of this first double leaf-trace are illustrated in Figs. 65-67. 
In older plants the double character of the leaf-trace is maintained, 
but each strand is surrounded by its own endodermis. This modification 
entails no additional complications at the actual exit of the trace, as will be 
seen below. As soon as the first double leaf-trace is completed the previous 
leaf-gap is repaired, and indications of the next appear in a breaking of the 
xylem arc into two portions, one considerably larger than the other. From 
each of these two vascular strands a portion is nipped off, each surrounded 
by its own endodermis, the structure of the older leaf-traces mentioned 
above being thus attained. The accompanying changes are indicated 
in Figs. 68-71. In Figs. 72 and 73 the two portions of the xylem are 
again joining, the junction being followed by a new split, to the horns of 
which the new leaf-trace is attached. Subsequent changes are merely 
a repetition and elaboration of the same process. 
The occurrence, in connexion with the third or fourth leaf-trace, 
of a strand of fundamental-tissue surrounded by an endodermis is of 
considerable interest. A single transverse section at this particular level 
exhibits a structure closely approximating to that of a typical c gamostele * 
as illustrated by the rhizome of Marsilia. Again, support is apparently 
afforded to Jeffrey’s hypothesis of the primitive amphiphloic stele with 
an internal endodermis. A mental picture of the whole region of the leaf- 
gap will, however, at once show these ideas to be erroneous. What we 
really have is the formation of a fundamental-tissue pocket which is 
ensheathed on all sides by an endodermal layer, and hence closely 
resembling the ‘ endodermal pockets ’ occurring in Schizaea dichotoma 
*S. malaccana 2 , and Lindsay a 3 . There can be no doubt that the first two 
or three small cells with yellowish glistening walls which appear in con- 
nexion with the third or fourth leaf-trace are really the endodermal cells 
sheathing the apex of the cone or elongated dome of ground-tissue laid 
down from the growing point in the medullary phloem 4 . 
In the above account, the roots have been practically omitted for 
the sake of brevity and clearness. It will be sufficient to say that the 
roots are perfectly normal, and that the leaf-traces are always formed, 
in young plants at any rate, directly over the position of the last root, 
and very soon after the latter has joined the stelar system. 
1 Boodle, Comparative anatomy of the Hymenophyllaceae, Schizaeaceae and Gleicheniaceae, iv. 
Further observations on Schizaea. Annals of Botany, xvii. 
2 Tansley and Chick, On the anatomy of Schizaea malaccana. Annals of Botany, xvii. 
3 Tansley and Lulham, On a new type of Fern-stele, &c. Annals of Botany, xvi. 
4 The term 1 fundamental-tissue pocket ’ or ‘ ground-tissue pocket ’ has been employed since the 
writer believes that such a term more correctly indicates the essential nature of the phenomenon. 
