Root Nodules in the Podocarpineae . 811 
group, those of Podocarpus and Microcachrys being most nearly alike, 
differing only in size, whilst Dacrydmm resembles Saxegothaea in the 
characteristic prolific formation of hairs, and Saxegothaea differs from all 
the rest in the extremely frequent branching not only of the root but also 
of the nodules. 
The genus Phyllocladus has led to considerable discussion as to its re- 
lationships, since it possesses some of the characters of both groups of the 
Taxaceae, namely, the Taxineae and the Podocarpineae, and consequently 
may belong to either of these groups, or it may be an intermediate group 
between them. Young has summarized the characters which it possesses 
that are common to these groups respectively, and has decided that the 
features which relate it to the Podocarpineae are more fundamental than 
those relating it to the Taxineae, and are also too fundamental to admit of 
its being placed in an intermediate group. The presence of root nodules, 
indicating the capability of the root to form a symbiotic association with the 
nitrogen-fixing organism Pseudomonas radicicola , in Phyllocladus , as well 
as in all the other genera of the Podocarpineae, is an additional character 
relating Phyllocladus with this group. 
In conclusion, I wish to thank the Director of the Royal Botanic 
Gardens, Kew, for supplying the material necessary for my work, and also 
Professor W. B. Bottomley for his suggestions and kindness during the pro- 
gress of these investigations, which have been carried out in his laboratory 
at King’s College, London. 
Summary. 
1. Root nodules are present in all the genera of the Podocarpineae 
examined, namely, Podocarpus , Microcachrys , Dacrydmm , Saxegothaea, and 
Phyllocladus . 
2. The nodules are modified lateral roots. They are perennial 
unbranched structures, except in Saxegothaea , where bifurcation frequently 
occurs. 
3. The outer layer of cells in the nodules is capable of producing non- 
septate hairs at the beginning of the second year’s growth in all the genera, 
but their presence is characteristic of the nodules Dacrydium , Saxegothaea , 
and Phyllocladus. 
4. The nitrogen-fixing organism Pseudomonas radicicola penetrates 
a root-hair and from thence enters the cortex of the root, where it propagates 
itself. 
5. The nodules, in all the genera, are produced by the infection of the 
meristematic tissue of the young root, before it emerges from the cortex of 
the parent root, by Pseudomonas radicicola. 
6. A mature nodule is traversed for about half its length by a small 
