I 12 
Bottomley , — The Root-nodules of Myrica Gale . 
Myrica Gale. 
The peculiar nodule formations on the roots of Myrica Gale were first 
described and figured by Brunchorst in 1886. He states that the nodules 
are caused by an endotrophic fungus with septate hyphae and terminal 
spores, and considered them simply disease formations. 
Moller in 1889 confirmed Brunchorst’s observations, and, without 
adequate reasons, placed the fungus in the group Frankia , naming it Frankia 
Brunckorstii , considering it to be closely related to a similar fungus said 
to occur in Alder nodules. 
Marshall Ward in 1889 mentions Myrica nodules as possible instances 
of symbiosis as yet unexplained. 
Tubeuf in 1896 speaks of the Mycodomatia of Myrica . He says the 
nodules ‘ may increase to very large tubers with surfaces resembling a bunch 
of grapes. In the large cells of the middle layers of the primary root-cortex 
of these growths, coils of very fine fungus-threads are sheltered ; these 
extend year after year into the younger parts of the enlarging tubercles, and 
gradually disappear in the older parts. What may be the significance of 
these structures for plants possessing chlorophyll and furnished with normal 
roots is as yet unknown.’ 
In 1902 Shibata stated that the inhabiting fungus is found exclusively 
in a peripheral sub-cork layer of parenchymatous tissue one to three cells 
thick, whilst the remaining parenchymatous cells of the rind are filled with 
starch bodies. Because of the peculiar ray branching of the fungus and its 
club-shaped spores he considered it to belong to the group Actinomyces . 
Peklo in 1910, working on material from plants grown in a greenhouse, 
supported Shibata’s views. 
External Structure of the Nodules. 
For the purpose of this investigation root- nodules of Myrica Gale were 
obtained from plants growing wild in Wales, Ireland, and the North of 
England, and from cultivated plants in the Chelsea Physic Gardens. The 
roots of all the plants were found to possess nodules of varying sizes. The 
young nodules (PI. XI, Fig. 1) are visible first as tiny swellings on the sides 
of the roots. These grow until they are from 2-3 mm. long and o-8-i mm. 
broad. In this stage they resemble the single nodules found on Vida saliva. 
This primary nodule then ceases to elongate, but from the distal end a thin 
hair-like rootlet grows out, and around this rootlet, from the body of the 
primary nodule, three secondary nodules arise. These secondary nodules 
grow to the size of the primary nodule and then each again gives rise to 
a rootlet and three tertiary nodules. These again repeat the process until 
by repeated branching the characteristic * cluster ’ nodules (Fig. 2), with 
their fringe of radiating rootlets, are formed. When the branches become 
