166 MR. P. GROOM—CONTRIBUTIONS TO THE 
and longitudinally extended parenchymatous cells. The proto- 
phloëm is erushed and stains bright blue with aniline-blue. 
The xylem is mainly constituted of tracheides forming an 
uninterrupted mass. "They have transverse pits. The tracheides 
are separated from the phloém by long parenchymatous cells. 
Here and there between the tracheides and the sheath are wood- 
parenchyma cells. In the larger central bundles the protoxylem 
is visible in the form of curious narrow vessels, having very loose 
thickenings (spiral, annular, reticulate), which may be described 
as tangled. A small intercellular space denotes that there has 
been an attempt to form the typical schizo-lysigenous inter- 
cellular space. In some of these larger bundles, radially within 
this protoxylem, there is a collection of elongated parenchymatous 
cells with narrow lumina which strongly resemble the phloém. 
I never succeeded in discovering sieve-tubes amongst these cells, 
though they possibly occur. Such bundles, then, are probably 
bieollateral. The outer vascular bundles are smaller, and near 
the general sheath some of them consist solely of phloém. 
In the uninjured axis I could detect the entrance of fungal 
hyphe ina few isolated spots, and the attacked cells acquired very 
thick suberized walls which soon prevented the hyphe penetrating 
more deeply. But part of the axis had been mechanically injured 
some distance up. The wound was closed over by a false epi- 
dermis. At certain points hyphe had penetrated and descended 
even as deep as the sheaths of the vascular bundles. The walls 
of the cells attacked had become decolorized and the contents 
disorganized and coloured brown. Of course it was impossible 
to decide whether or not these hyphe belonged to the mycorbizal 
fungus. The injury undoubtedly was not initiated by a fungus. 
This shows that the thick cuticularized epidermal walls normally 
can act as a shield to ward off fungal attacks. 
This account of the structure of the middle part of the inflores- 
cence-axis holds for the rest of the axis, except for some differ- 
ences with reference to the mechanical cells, raphide-mucilage 
cells, and the distribution of starch. 
At the basis of the axis, mechanical cells with wide lumina form 
two or three layers round the general sclerenchyma-sheath ; these 
disappear higher up the axis. But an interesting change in 
structure again takes place at the region of attachment of each 
fruit. In relation to the diameter of the axis, the fruits are 
disproportionately large and heavy because of the large amount 
of water in them. We might anticipate that additional pro- 
