766 de Bruyn .— The Ontogenetic Development of the 
shoe-shaped stele, with the endodermis invaginated, while higher up the 
endodermis and pericycle form a straight line on the adaxial side. In some 
of the petioles of this stage a tissue of sclerenchymatous cells, surrounded 
by an endodermis, is found in the centre of the petiolar stele. These steles 
show a very close resemblance to those in the base of the petioles of Matonia 
sarmentosa (Compton ] ), and of some species of Gleichenia (Poirault 2 ). This 
structure is not found through the whole petiole but only in parts of it, and 
is not always the same in different leaves. In one petiole, e. g., the whole 
stele has horseshoe-shaped structure at the base. Then the ends of the 
limbs of the horseshoe approach each other till they meet. The endo¬ 
dermis of both ends joins together, and attached to it is a loop of endodermal 
cells, including a strand of ground tissue. The loop becomes detached from 
the outer endodermis, and thus a patch of sclerenchyma surrounded by 
a ring of endodermal cells is formed inside the stele. These endodermal 
cells are at first separated by only one layer of pericyclic cells from the 
endodermis surrounding the stele, but soon the patch of sclerenchyma with 
its endodermis is found more in the centre of the stele. This structure is 
reached at 0-5 cm. from the base. The resemblance to Matonia sarmentosa 
and some species of Gleichenia is now very striking. At a higher level 
more changes take place. The outer endodermis projects somewhat inwards, 
and the internal sclerenchyma changes its position more towards the adaxial 
side of the petiolar stele. Finally the inner and outer endodermis come into 
connexion with each other, and a normal horseshoe-shaped stele is again 
present at 1*5 cm. from the base. For a distance of 1*25 cm. this structure 
remains ; then the ends of the limbs of the horseshoe approach each other 
again, and at 3 cm. from the base there is again internal sclerenchyma ; but 
now only one cell, surrounded by endodermis, is present inside the stele. At 
3*5 cm. the number of sclerenchymatous cells has increased to three. At 
a higher level it was impossible to tell if internal sclerenchyma or endo¬ 
dermis were still present, but the outer endodermis still formed a straight 
line at the adaxial side. Unfortunately the petiole was broken off at this 
point. At the highest level starch was still present in the stelar tissue. 
At the base of another petiole, 5 cm. long, the endodermis and pericycle 
formed a straight line on the adaxial side. Inside the stele one or two dark 
cells were present which might be internal endodermal cells. Soon a whole 
group of these internal endodermal cells was formed, and in the midst of 
these one or two sclerenchymatous cells appeared. The sclerenchymatous 
cells surrounded by the endodermis come nearer to the outer endodermis 
and come into connexion with it. After some time they are separated 
again from the outer endodermis by a layer of pericyclic cells, and 
1 R. H. Compton : The Anatomy of Matonia sarmentosa , Baker. New Phyt., vol. viii, 1909, p. 302. 
2 Poirault: Recherches anatomiques sur les Cryptogames vasculaires. Ann. des Sciences nat. 
(Bot.), sdrie vii, tome 18, 1893, p. 1S1. 
