EXPLANATION OF TERMS. 
Theca. Same as ascus. 
Thecaspore. Same as ascospore. 
Thermotropism. Phenomena induced 
in a growing organ by the influence of 
conditions of temperature. 
Thrush. Disease of the mucous membrane 
ofmouth,throatandoesophagusinchildren 
characterised by formation of pustules 
due to Saccharomyces albicans, Reess. 
Same as aphthae. 
Tinea tonsurans. Same as ringworm. 
Torulose. Swollen at intervals. 
Trama. In Basidiomycetes: middle tissue 
in the projections or septa of the sporo- 
phore which bear hymenium. Same as 
dissepiment, intralamellar tissue. 
Tremelloid. Resembling Tremella. 
Trichogyne. Thread-like receptive portion 
developed as part of an archicarp. 
Trophoplast. Same as plastid. 
Trophotropism. Phenomena induced in 
a growing organ by the influence of the 
chemical nature of its environment. 
Tube-germination (Schlauchkeimung). 
Germination of a spore in which the first 
product is a germ-tube. Comp. sprout- 
germination. 
Tubulus. (a) In Pyrenomycetes : Same as 
neck. (4) In Hymenomycetes: tube 
lined with hymenium on the surface of a 
pileus. Same as pore. 
Unicellular. Formed of one cell. 
Uredo. Hymenium producing uredospores 
only. Termed also uredo-layer. 
Uredogonidium. Same as uredospore. 
Uredospore. In Uredineae : spore formed 
by acrogenous abjunction on a sterigma 
from which it separates when mature and 
on germination produces a mycelium 
bearing uredospores or uredospores and 
teleutospores. 
Uterus. In Gastromycetes: same as peri- 
dium, 
Veil. Same as velum. 
Veines aériféres. Same as venae in- 
ternae. 
Veines aquiféres. Same as venae ex- 
ternae. 
Velum. In Hymenomycetes: special 
envelope within which the growth of the 
whole or a portion of the sporophore 
takes place. Same as veil, involucrum 
of Persoon. By Persoon applied to what 

501 
is defined above as cortina. See 
marginal veil, velum universale. 
Velum partiale. Same as marginal 
veil. See velum. 
Velum universale. In Hymenomycetes 
sac enclosing the whole of a sporophore 
as it grows and ultimately ruptured atthe 
apex by the unfolding pileus. Same as 
volva. See velum. 
Venae externae. In Tuberaceae: white 
veins seen on section of the sporophore 
produced by dense tissue containing air 
and filling the asciferous chambers. 
Same as veines aériféres. Comp. 
venae internae. £ 
Venae internae. In Tuberaceae: dark- 
coloured veins seen on section of the 
sporophore indicating the walls of as- 
ciferous chambers, which are composed 
of tissue containing no air. Same as 
venae lymphaticae, veines aquiféres. 
Comp. venae externae. 
Venae lymphaticae. Same as venae 
internae. 
Volva. Same as velum universale, 
Witches’ broom. Disease on the silver-fir, 
birch, cherry,and other trees characterised 
by the development of a tangle of shoots 
in a tuft and due to the attack of Peri- 
dermium elatinum or of Exoascus. 
Woronin’s hypha. In Ascomycetes: a 
coiled hypha found in some forms at the 
place where the sporocarp subsequently 
developes and probably homologous with 
an archicarp. 
Xyloma. Sclerotioid body of varying 
shape which does not send out branches 
developing into sporophores but produces 
sporogenous structures in its interior. 
Yeast-fungus. Species of Saccharomyces. 
Sometimes used as equivalent to the 
growth form distinguished as Sprouting 
Fungus, but this misuse leads to con- 
fusion. 
Zoogloea. In Schizomycetes: colony 
imbedded in a gelatinous substance. 
Zoospore. Motile spore. 
Zygospore. Immediate product of conju- 
gation of two similar gametes. 
Zygosporophore. In Mucorini: same as 
suspensor. 
