GLOSSARY 
429 
Perfoliate.—Applied to leaves which are united around the stem at their base. 
Perianth.—The floral envelopes, calyx and corolla or calyx alone when corolla 
is absent. 
Per'iblem.—A region of meristem lying between the dermatogen and plerome 
in the growing end of a root or stem. The meristem which gives rise to 
cortex. 
Pericam'bium.—A zone of meristematic tissue lying just within the endodermis. 
Pericarp.—The wall of a ripened ovary or fruit surrounding the seed or seeds. 
Pericla'dium.—A sheathing petiole. 
Perlcycle.—A zone of formative tissue lying outside of the fibrovascular region 
and inside of the endodermis. 
Periderm.—The cork tissue of plant axes. 
Peridlum.—The outer covering of certain fungus fructifications as puff-balls. 
Per'igone.—See perianth. 
Perig'ynous.—Applied to stamens and petals when they are adherent to the 
calyx throat, and so borne around the gynoecium. 
Perlsperm.—The nourishing tissue of some seeds outside of the embryo sac and 
representing the nucellus of the ovule, which, during maturation has be¬ 
come laden with nutriment. 
Peristome.—The teeth around the mouth of the capsule in mosses. 
Perithe'cium.—The receptacle containing asci in certain Ascomycetes. 
Persist'ant.—Applied to parts of the flower which remain until the fruit ripens 
or to leaves which remain on the plant over winter. 
Per'sonate.—Applied to a bilabiate corolla which has its throat closed by a con¬ 
vex projection on the base of the lower lip. 
Pet'al.—One of the floral leaves of the corolla. 
Pet'aloid.—Of some other color than green. Having the color of a petal. 
Petiole.—A leaf stalk. 
Pet'iolule.—The stalk of a leaflet. 
Phelloderm.—Secondary cortex containing chloroplasts formed by the cork 
cambium on its inner face. 
Phellogen.—The meristem-which gives rise to cork and frequently secondary 
cortex; cork cambium. 
Phlo'em.—That part of a fibrovascular bundle which contains sieve tissue and 
frequently bast fibers. 
Phloroglu'cin.—A white crystalline substance having the formula of C 6 H 6 0 3 , 
obtained by the decomposition of phloretin and from certain gummy ex¬ 
tracts and used with hydrochloric acid as a test for lignin. 
Phycocy'anin.—The blue pigment found in the Cyanophyceae (Blue Green Algae). 
Phycceryth'rin.—The red pigment occurring in the Rhodophyceae (Red Algae). 
Phycophae'in.—The brown pigment found in the Phycophyceae (Brown Algae). 
Phycoxan'thin.—A yellowish pigment occurring in some Algae. 
Phyllocla'de.—A flattened branch which resembles a leaf as in Ruscus. 
Phyllode.—A dilated petiole. 
