Root Nodules in the Podocarpineae. 809 
bifurcation. The rupture and subsequent shedding of the old outer nodular 
tissue when two nodules are produced in place of the old ones also adds to 
the possibilities of hair production by the surface cells. The old protecting 
layers having disappeared, the outer cells of the new nodules can, on reach- 
ing maturity, grow out into these structures. This explains the apparently 
more constant appearance of hairs on the nodules of Saxegothaea than on 
those of the other genera, because, on any portion, this method of branching 
makes it probable that there will be many nodules present which are only 
one year old, and which will probably be sending out hairs. 
In their method of growth the nodules of the Podocarpineae differ from 
all other root nodules with which they are associated. The leguminous 
nodules are annual structures and are not modified roots, and the non- 
leguminous nodules of the Cycadaceae, Elaeagnaceae, Alnus , and Myrica 
. are modified roots with a perennial- habit, each possessing an apical 
meristematic region, by means of which their growth is continued from 
year to year. The nodules of the Podocarpineae, although perennial modi- 
fied roots like the latter, are unique in having no persistent meristematic 
zone, the tissue definitely functioning for one year only. The formation of 
new tissue is always endogenous in this group, a new nodule being formed 
inside the old one year after year, whilst in the other non-leguminous nodules 
the growth is continued at the apex. 
The nodules of the Podocarpineae are typically simple structures, whilst 
those of other non-leguminous plants are characteristically branched. The 
bifurcation of the nodule which occurs in Saxegothaea , as described above, 
recalls the branched nodules of the Cycadaceae, Elaeagnaceae, and Alnus , 
but in these there is no breaking through of old tissue ; this latter occurs 
in Myrica , when the stele continues its growth and eventually penetrates 
the nodule, emerging as a small root. There is, however, no other known 
case where the original nodule, by branching, becomes replaced, as it does in 
Saxegothaea , by two apparently simple nodules. 
The outer zones of dead empty cells in the old nodules provide a suit- 
able substratum for the development of various Fungi, and in Podocarpus 
one sometimes finds true fungal hyphae in these cells. Some of these have 
probably been described by other observers, and may, indeed, as they 
suggest, be of a mycorhizal nature, forming a symbiotic association with 
the roots of the plant, but they are evidently not concerned with the forma- 
tion of the nodules. This conclusion is supported by the production of root- 
hairs on the nodules at the beginning of their second year’s growth, which 
sometimes occurs in Podocarpus Totara , Podocarpus elongata , Podocarpus 
Chilina , and Microcachrys tetragona , usually occurs in Podocarpus alpina , 
and always occurs in Dacrydium Franklini , Saxegothaea conspicua , and 
Phyllocladus trichomanoides . Shibata, however, does not suggest that the 
fungus he describes causes the formation of the nodules, because he remarks 
