nmm sP

THE BRITISH SMUT FUJJGI 57
from one node to the next and frequently aflFecting several successive intemodes
or the entire stem (Plate I, Fig. 5), no special covering membrane but at first
protected by the leaf sheaths; occasionally in the spiltelets. Spore mass powdery,
dark brown, weathering away to leave the culm bare. Spores spherical to ovoid,
sometimes more irregular, not infrequently, especially in some collections with
a rather inconspicuous transparent cap at each pole, yellow-brown, smooth,
4-7 (av. 4-5-5-0 ;LI) diam.i
On Agropyron acutum, A. caninum, A. juncewm, A. pungens, A. repens
Ammophila arenaria, Bromus carinatus, B. erectus, Elymus arenarius, Festuca
gigantea, Trisetum flavescens.
June-Sept. Widespread. Common.
Exsiccati: Cooke, Fungi Brit. Exsic, i, 56; ii, 433; Vize, Fungi Brit., 35. Sydow,
Dstilagineen, 10; Vestergren, Micromycetes rar. select.^ 1595.
Spore germination. Several workers refer to the difficulty of germinating spores
of this species (Fischer von Waldheim, 1869; Plowright, 1889; Viennot-Bourgin,
1937; Bond, 1940). Winter (1876) figured a septate promycelium with one sporidium
or a. TeMiveiy long Bierigma^ while BreMd (1^83) and Boss (1927}foand
that the spores produced only a richly branched mycelium. Fischer & Hirschhom
(1945 b) have photographed the germination of stem smut from
several American forage grasses (Fig. 2 g). The proniyceUa become septate and
put out protuberances which usually develop into branches. Occasionally (see
Fig. 2gr (lower fig.), from Agropyron spicatum) these branches end in a sporidium,
thus confirming some of the older conflicting records. In cultures branches grow
above the medium and form chains of aerial sporidla (Boss, 1927; Bomhovd,
1936; Kolk, 1943; Fischer & Hu-schhorn, 1945 b). Bornhovd paired 20 monosporidial
cultures ^d failed to observe hyphal fusion, though the presence of
coarser hyphae (Siichfaden) in old cultures suggested that fusion had occurred.
Fischer & Hirschhom (1945 b) record fusions between detached sporidia.
Infection of the host. The inoculation experiments of Bomhovd (1936) and Bond
(1940) were inconclusive. Fischer (1945) successfully infected mature plants of
Elymus canade^isis; Agropyron trachycaulum, and A. cristatum. The plants were
clipped back in August to about five in., sprayed with a suspension of spores, and
kept moist for 48 hours. The smut did not sporulate until two or three years
after inoculation. The failure of other methods of inoculation, namely, blossominfection
and seed-contamination, showed that this ^mut is not seed-borne.
The morphology and growth of the sterile leafy culms replacing normal
inflorescences on infected plants of Bromus erectus £(,nd Elymus arenarius have
been described by Feucht (1930) and Bond (1940). Infection is systemic and a
perennial mycelium exists in the rhizome. In diseased plants the shoot follows
a continuous development in contrast to the periodic growth of healthy rhizomes.
Viennot-Bourgin (1937) has described the changes in anatomy induced
in the host by this smut.
^ This description was written before the publication of the paper by Fischer & Hirschhom
(1945 b), in which V. hypodytes is considered to embrjice four species and one variety
separable into two groups characterized by species whose spores possess or lack hyaline
bipolar areas or appendages. After a re-examination of the JBritish material and a study of
other collections from Europe and North America, it was decided to make no change at
present in the taxonomy and nomenclature of this smut.