7 1 6 Boodle. — Anatomy of the G teicheuiaceae. 
between the tips of the hooks. The protoxylem groups have 
the usual positions. A few sclerotic elements are found in 
the phloem on the outer side of the xylem, chiefly opposite 
the lateral protoxylems. 
Poirault (’ 93 , p. 190) mentions as a distinguishing character, 
that all the species of Eugteichenia except G. Boryi possess 
strongly lignified, pitted or reticulate cells in the pericycle of 
the petiole, while in Mertensia such cells occur only isolated, 
or in the majority of species are completely absent. This 
cannot be held as a reliable distinction. Among species of 
Eugteichenia , G. dicarpa showed lignification and slight 
thickening of its pericyclic cells, and G. dicarpa , var. alpina , 
had a pericycle composed entirely of pitted and strongly 
sclerotic cells 1 . G. dicarpa, var. longipinnata , also has a 
sclerotic pericycle. On the other hand, sclerotic pericyclic 
cells were not observed in G. circinata , though they were 
found by Poirault in G. rupestris , which is to be regarded 
as a variety of this species. Turning to Mertensia , G. crypto - 
carpa has its pericycle sclerotic throughout as in G. dicarpa , 
var. alpina , though not quite so thick-walled. As G. crypto - 
carpa and G. dicarpa , var. alpina , are both distinctly xerophytic, 
it appears probable that xerophytic habit may produce a 
strongly sclerotic pericycle in both subgenera, though Eu- 
gleichenia may have a more general tendency to form it than 
Mertensia. « 
We may now deal with the petiole of Mertensia. Some 
of the species have much larger petioles and petiolar bundles 
than are found in the other subgenus. The type of structure 
of the bundle may be said to be much the same as in 
Eugteichenia , with the exception that the endodermis is 
invaginated, so as to follow to some extent the outline of the 
xylem-arch, and so that the central region is occupied by 
sclerotic tissue continuous with the cortex, and apparently 
belonging to it, instead of to the pericycle as in G. dicarpa . 
Thus the bundle is arched, or in several species roughly C- 
1 Some of the more external of these had their walls slightly tinged with 
the brown colouring matter, which usually characterizes the cortical sclerenchyma. 
