756  . PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
The structure of the xylem is essentially similar to that of the petiolar bundle of 
Lyginodendron. The majority of the tracheides are spiral or reticulate, but some 
are pitted. ‘The lax spiral elements (protoxylem) lie in the interior of the strand. 
The structure of the cortex of the petioles has been sufficiently described above. 
One point remains to be discussed ; in two, at least, of the preparations, sporangia, 
like those of certain Ferns,* are found in association with Heterangiwm foliage.t A 
portion of one of these preparations is represented in fig. 23. The sporangium, sm., 
is in close contact with a fragment of leaf, which appears to be continuous with a 
small petiole of Heterangium. If the continuity between the sporangium and the 
leaf could be established, the fact would be of the greatest importance. Careful 
examination of the preparation, however, leads us to doubt much whether this was 
the case. The fragment is in bad condition, and we found it impossible to prove that 
the shred of tissue on which the sporangium is seated, really. belonged to the 
Heterangium foliage. 
The other preparation in question (C.N. 1292) contains numerous sporangia, none 
of which, however, are connected with the foliage. This slide contains petioles of 
Rachopteris Oldhamia, WiLL, as well as of the Heterangium, so that here it is plain 
that no definite conclusion can be drawn. In other cases seeds have been found in 
association with specimens of Heterangium,{ but there is not the slightest reason for 
supposing that they have anything to do with our plant. Here, again, the question 
of fructification must for the present remain undecided. ‘ 
Our conclusions as to the foliage of Heterangium Grievii are the following :— 
1. The leaves were arranged spirally on the stem, the phyllotaxis being usually 
either 2 or 2. 
2. The leaves were repeatedly compound, with long and much-branched petioles, 
bearing small leaflets. 
8. The petiole contained a single vascular bundle of concentric structure. 
4. The cortex was characterized by the horizontal sclerotic plates in its inner zone 
and by the “ Dictyoxylon” structure of its external portion, — 
5. Both in form and structure, so far as they can be determined, the leaves of 
Hetevangium closely resembled those of Lyginodendron and were of a Fern-like 
character. 
C. Ture Root. 
1. Connection between Root and Stem. 
Several specimens of Heterangium Grievit show adventitious roots in connection 
with the stem. Two such specimens have been previously figured, both of which are 
* Cf. Wituiamson, “ Organization,” Part VIII., Plate 7, fig. 29, 
+ C.N. 1287 and 1292. 
{ C.N. 1915 D, G, H, and O. 
