528 Gwynne- Vaughan.—Some Remarks on the 
Once formed the pith rarely disappears again. In two cases, however, 
the xylem became solid once more above the level of the seventh leaf. 
This seems to happen more frequently in Osmunda cinnamomea . Indeed, 
in this plant the transitional region of the sporeling seems to be much more 
drawn out and extended than in O. regalis , for Faull finds protostelic leaf- 
trace departures as high up as the seventh or eighth leaf, and he says that 
a permanent pith is not attained until about the level of the twentieth. 
Detailed Structure of the Sporeling. 
In both Osmunda and Todea the foot of the sporeling forms a massive 
protuberance and is prolonged laterally into two wings which are wrapped 
round the stem like stipules. In sporelings of some age the cells of the 
central tissue of the foot become quite thick-walled. The endodermis of 
the stele usually shows a slight projection on the side towards the foot. 
The amount of xylem in the stele varies considerably with the strength 
and vigour of the individual sporeling. Just below the first leaf it consists 
on an average of about eighteen tracheae, below the second about 20-30 are 
present, and below the third it may contain as many as forty. The largest 
mass of solid xylem without any trace of parenchyma amounted to fifty 
tracheae. The xylem-sheath is relatively stout in the Osmundaceae as an 
order, and it is already well developed in the sporeling, being from two to 
four cells wide in the protostelic region. The phloem is well formed from 
the first and consists of one, rarely two, rows of rather large sieve tubes. 
No porose layers were found in the earlier formed regions of the stem. The 
pericycle is at first a single layer which is sometimes interrupted so that 
a sieve tube may be in direct contact witli the endodermis. The endodermis 
is clear and distinct from the very first, but it is not differentiated beyond 
the simplest type of endodermis ; that described by Kraemer as a ‘ primary 
endodermis’. 1 It is interesting to note that according to Rumpf 2 and 
Basecke 3 the endodermis remains in the primary condition in this order, in 
the Ophioglossaceae and Marattiaceae, while in the other Filicales it 
differentiates into a more advanced type of structure. Caspary’s band is 
usually well formed, but is sometimes badly delimited, extending also over 
the tangential walls. It does not appear to be cutinized or suberized, but 
gives all the reactions usually associated with the presence of lignin. The 
contents of the endodermal cells take up certain stains such as methylene 
blue and iodine green with especial avidity, apparently owing to the 
1 Karl Kraemer: Wurzelhaut, Hypodermis und Endodermis der Angiospermwurzel. Biblio¬ 
theca Botanica, 1903, Heft 59, p. 87. 
2 Georg Rumpf: Rhizodermis, Hypodermis und Endodermis der Farnwurzel. Ibid. 1904, 
Heft 62, p. 25. 
s Paul Basecke : Beit. z. Kennt. der physiologischen Scheiden der Filicineen-Achsen, &c., 
p. 12. Inaug. Dissert., Marburg, 1908. 
