Mycorrhizal Infection of Germinating Seedlings of 
Nothofagus solandri var. cliff ortioides (Hook f.) Poole 
B. C. Arnold 1 
In THE COURSE of studying the anatomy of roots 
of the evergreen tree, Nothofagus solandri var. 
cliff ortioides, regular observations were made 
on the natural germination of seedlings in a 
small tract of forest in the vicinity of the Uni- 
versity of Canterbury Mountain Biological Sta- 
tion at Cass. The area concerned is about 2 
acres in extent, at an altitude of 2,000 ft. above 
sea level, isolated in a gully from the main 
forest areas of N . solandri var. cliff ortioides 
which dominate the wetter mountainous region 
a few miles to the west. Rainfall over a 12- 
month period was 47.9 in. The soil is a mixture 
of clay and greywacke covered by humus and 
moss. Growth of the seedlings was inspected at 
fortnightly intervals over a period of 18 months. 
The mycorrhizas of N. solandri var. cliff ort- 
ioides are similar in a general way to those of 
Fagus sylvatica (Harley, 1937: 421-423) but 
are somewhat smaller, and do not give rise to 
the "intense racemose” type (Harley, 1937: 
421-423). 
Four months after germination had com- 
menced, a drought of more than 2 weeks was 
encountered, during which newly formed my- 
corrhizas shrivelled, many seedlings wilted, and 
a large proportion died. It was not apparent 
whether this circumstance had any radical in- 
fluence on the degree or course of subsequent 
mycorrhizal infection. 
Microscopic examination was made of intact 
root and mycorrhiza surfaces as well as of 
serial transections and longisections, in an at- 
tempt to follow the pattern of mycorrhizal in- 
fection of the seedlings. The present investiga- 
tion was incidental to anatomical studies of my- 
corrhizas to be reported elsewhere. 
1 Department of Botany, University of Canterbury, 
Christchurch, New Zealand. Manuscript received April 
24 , 1959 - 
GERMINATION AND INFECTION 
At the time of the emergence of the radicle, 
in spring, the blackened seed coat was gen- 
erally enmeshed in mycelial threads of several 
different types. The testa was intact except at 
the point of emergence of the radicle, but in a 
state of superficial decay. In serial microtome 
sections of the seed, no sign of fungal infection 
of the expanding embryo was to be seen. 
As the radicle grew ahead through moss or 
leaf mould, hyphae of different colour and form 
traced rather sparsely over the smooth surface 
of the root, which maintained a fairly constant 
diameter of about 0.75 mm. With the appear- 
ance of the piliferous layer, however, a more 
copious growth of fungi took possession of the 
radicle and became inextricably entangled in the 
elongating root hairs. 
Clamp connections were evident in several 
of the different types of fungi. Among these 
was a species constantly present and notable 
for its long, solitary hyphae, even septation, dis- 
tinct clamps, and thick golden-brown walls. This 
fungus appears to have no role in the formation 
of N. solandri var. cliff ortioides mycorrhizas, al- 
though it may be a regular occupant of the 
rhizosphere of the tree. 
Regions of the radicle lacking root hairs were 
less densely overgrown with fungi than was the 
piliferous zone. 
After 3 or 4 weeks growth of the seedlings 
(by which time the cotyledons were well ex- 
panded), broad sheets of coherent hyphae, in 
roughly parallel strands, were found connecting 
the seedling roots with mycorrhizas of nearby 
trees, from which they had apparently emanated. 
Most of the fungal wefts joining old my- 
corrhizas and the root surface of seedlings were 
white or colourless. In the course of growth, the 
radicles came also in contact with violet, yellow, 
248 
