Glossary - Westcott's Plant Disease - page 697

Sporidium , pl. Sporidia . Basidiospore of rusts
and smuts.
Sporodochium , pl. Sporodochia . Cluster of
conidiophores interwoven on a stroma or
mass of hyphae (Fig. 5, p. 43).
Sporophore . Spore-producing or supporting
structure - fruit body; used especially in the
Basidiomycetes (Fig. 5, p. 318).
Sporulate . To produce spores.
Sprayer . Apparatus for applying chemicals in
liquid form.
Sterigma ,pl. Sterigmata . Projection for supporting
aspore.
Stipe . A stalk. Stipitate . Stalked.
Strain . An organism or group of organisms
differing in origin or minor aspects from
other organisms of same species or variety.
Stroma , pl. Stromata . Mass of fungus hyphae
often including host tissue containing or bear-
ing spores.
Subiculum , Subicle . Netlike woolly or crustlike
growth of mycelium under fruit bodies.
Substrate . The substance or object on which
a saprophytic organism lives and from which
it gets nourishment.
Suscept . A living organism attacked by, or sus-
ceptible to, a given disease or pathogen; in
many cases a more precise term than host but
less familiar.
Susceptible . Unresistant, permitting the attack of
a pathogen.
Swarmspore . Zoospore.
Synnema , pl. Synnemata . Groups of hyphae
sometimes joined together, generally upright
and producing spores; coremium.
Systemic . Term applied to disease in which single
infection leads to general spread of the patho-
gen throughout the plant body; or to a chemical
that acts through the vascular system.
Teleomorph . State of life-cycle in which spores
are formed after nuclear fission.
Teliospore . Winter or resting form of rust spore,
from which basidium is produced (Fig. 1,
p. 344; Fig. 2, p. 349; Fig. 3, p. 353).
Telium . Sorus producing teliospores.
Thallophyte . One of the simpler plants, belonging
to the algae, bacteria, fungi, slime molds, or
lichens.

Thallus . Vegetative body of a thallophyte.
Tolerant . Capable of sustaining disease without
serious injury or crop loss.
Toxin . Poison formed by an organism.
Tylosi , pl. Tyloses . Cell outgrowth into cavity of
xylem vessel, plugging it.
Urediospore . Summer spore of rusts; one-celled,
verrucose (Fig. 1, p. 344).
Uredium . Sorus producing urediospores.
Valsoid . Having groups of perithecia with beaks
pointing inward, or even parallel with surface,
as in valsa.
Vector . An agent, insect, man, etc., transmitting
disease.
Vein - banding . Symptom of virus disease in
which regions along veins are darker green
than the tissue between veins.
Verrucose . With small rounded processes or
warts.
Viroid . The smallest known viruslike infectious
agent having no protein coat and only a small
amount of nucleic acid.
Virulent . Highly pathogenic; with strong capacity
for causing disease.
Viruliferous . Virus-carrying; term applied partic-
ularly to virus-laden insects.
Virus . An obligate parasite capable of multiply-
ing in certain hosts, ultramicroscopic,
recognizable by the effects produced in
infected

hosts. Has nucleic acid with

protein coat.
Wilt . Loss of freshness or drooping of plants due
to inadequate water supply or excessive tran-
spiration; a vascular disease interfering with
utilization of water.
Witches ' Broom . Disease symptom with abnor-
mal brushlike development of many weak
shoots.
Yellows . Term applied to disease in which
yellowing

or chlorosis is a principal

symptom.
Zoospore . A swimming spore, swarmspore,
capable of independent movement (Fig. 1,
p. 35).
Zygomycetes . Subclass of the Phycomycetes,
characterized by gametes of equal size.
Zygospore . Resting spore formed from the union
of similar gametes (Fig. 2, p. 36).