498 
Pellicula. Theseparablerind-layersofsome 
compound sporophores. Same as cutis. 
Penicellate. Having the form of a pencil 
of hairs. 
Periderm. The cork-cambium and its 
products. 
Peridiolum. In Nidularieae: chamber 
of the gleba, forming a nest of spores, 
free or attached by a funicle within the 
peridium of the sporophore. 
Peridium. General term for the outer en- 
veloping coat of a sporophore upon which 
the spores develope in a closed cavity. 
InUredineaeit envelopestheaecidium and 
is also termed pseudoperidium, para- 
physes-envelope. In Gastromycetes 
termed also uterus, and may be differen- 
tiated into peridium externum (outer 
peridium), the outermost layer which 
opens in various ways and separates from 
the peridium internum (inner peri- 
dium)a layer directly enclosing the gleba. 
Peridium externum. See peridium. 
Peridium internum. See peridium. 
Periphysis. In Pyrenomycetes: sterile 
capilliform hyphal branch projecting 
from the wall of the pyrenocarp where 
there is no hymenium into its cavity. 
Periplasm. In Peronosporeae: protoplasm 
in the oogonium and the antheridium 
which does not share in the conjugation. 
Comp. gonoplasm. 
Perithecium. Same as pyrenocarp. 
Phototactic. Taking up a definite position 
with reference to the direction of incident 
rays of light. 
Phylogeny. Development of a species or 
larger group. 
Pileus. In Hymenomycetes: primarily, 
the conical or dome-shaped upper portion 
of the compound sporophore bearing a 
hymenium on its under side; now ex- 
tended to all compound sporophores 
in which the hymenium looks to the 
ground. Same as cap. 
Pityriasis versicolor. Disease of the 
skin caused by Microsporon furfur, Rob. 
Plasmodium. In Mycetozoa: body of 
naked plurinucleated protoplasm exhi- 
biting amoeboid motion. 
Plasmatoparous. In  Peronosporeae : 
forms are plasmatoparous when in ger- 
mination the whole protoplasm of a goni- 
dium issues as a spherical mass which at 
once becomes invested with a membrane 
and then puts out a germ tube. 
Plastid. Small variously shaped portion 
of protoplasm of a cell differentiated 
as a centre of chemical activity. 
Pleomorphism or Pleomorphy. The 
occurrence of more than one independent 
form in the life cycle of a species. 
Pleuroblastic. In Peronosporeae: forms 

EXPLANATION OF TERMS. 
producing vesicular lateral outgrowths 
serving as haustoria are pleuroblastic. 
Pluricellular. Composed of two or more 
cells. 
Plurisporous. Having two or more spores. 
Podetium. In Cladonieae: stalk-like or 
shrubby branched outgrowth of the 
thallus bearing exposed hymenia. 
Pollinarium, Same as cystidium. 
Pore. (a)In Pyrenomycetes: sameas ostiole. 
(6)In Hymenomycetes : same as tubulus. 
Primary lamella of spore. Outermost 
layer of the coats of a spore representing 
the original delicate wall of the primordial 
spore. 
Primordium, 
structure. 
Procarp. An archicarp with a special 
receptive apparatus, the trichogyne. 
Promycelium. Short and short-lived 
product of tube-germination of a spore 
which abjoints acrogenously a small 
number of spores (sporidia) unlike the 
mother-spore and then dies oft. 
Prosporangium. In Chytridieae: vesi- 
cular cell the protoplasm of which passes 
into an outgrowth of itself, the sporan- 
gium, and becomes divided into swarm- 
First beginning of any 
spores. 
Prothallium. A thalloid oophyte or its 
homologue. 
Protothallus. Same as hypothallus. 
Pseudoparenchyma. Symphyogenetic 
cellular tissue. 
Pseudoperidium. See peridium. 
Pseudopodium. In Mycetozoa: a pro- 
trusion of the protoplasm of an amoeboid 
body which may be drawn in or into which 
the whole mass may move. 
Puffing (stäuben). Sudden discharging of 
a cloud of spores. 
Pullulation. Same as sprouting. 
Pulvinate. Having the form of a cushion. 
Pycnidiophore. Compound sporophore 
bearing pycnidia. 
Pyenidium. In Ascomycetes: a variously 
shaped cavity resembling a pyrenocarp 
formed on the free surface of a thallus 
and containing gonidia which are termed 
pycnogonidia. See receptaculum. 
Pyenogonidium. Gonidium produced in 
a pycnidium. Same as pycnospore, 
stylospore. 
Pyenospore. Same as pyenogonidium. 
Pyrenocarp. Cup-shaped ascocarp with 
the margin incurved so as to form a 
narrow-mouthed cavity. Same as peri- 
thecium. 
Receptacle (receptaculum). Term of 
varying signification, most usually imply- 
ing a hollowed-out body containing other 
bodies. Has the following special appli- 
