* 
8 BRYOLOGY OF NEW ZEALAND. 
respect as between the leaves of a single stem; in such cases it is usually 
should also greatly deprecate laying undue stress on the length of the 
stem, as is done now and again by C. Miiller in the “ Symbolae ad Bryologiam 
Australiae” (Hedwigia, 1897). The general robustness and, within limits, 
the height of the stem may no doubt have specific value, but they must 
not be pressed too. far. 
e structure of the nerve, as seen in transverse section, is, as pointed 
out by Renauld, of importance. I give a brief outline of the structure of 
the four types described by him in the “ Essai sur les Leucoloma.” Thése 
will be found figured on Plate IV. 
I. ToxonEuron (fig. 17).—Nerve broad and rather flattened. Deuter 
cells central, numerous (7-14); stereids numerous, in two ands, one 
above and one below the deuter. (Examples, D. setosum, D. robustum, 
D. Menziesii. . 
Il. Hereronevuron (fig. 18).—Intermediate between Toxoneuron and 
Leptoneuron types. ariable in width, but usually narrower than in I; 
thin and flattened or somewhat prominent at back; deuter 4-5, central ; 
stereids wanting or very few, not forming distinct internal stereid bands. 
(Examples, D. plurisetum, D. cylividropyzis.) 
Ill. Lepronevron (fig. .—Nerve very narrow, flattened ; deuter 
central, 2 only ; stereids none, or here and there one between two adjacent 
epidermal cells. (Examples, D. Billardieri, D. fasciatum. 
CYRTONEURON (fig. 20).—Nerve moderately broad, thick and pro- 
minent behind, with two ridges of 
each side of the median line, forming ru mentary wings, so that in section 
it appears trapezoidal with prominent angles, each of 2-3 cells similar to 
the deuter; deuter central, 4, forming an are; the remainder of the tissue 
mi dD, ngens 1s given by 
Renauld as wi eroneuron nerve (while D. setosum has the Toxoneuron 
type), and I have found this to be the case with specimens determined 
