920 



GLOSSARY. 



Periblem, the embryonic tissue at a growing point 

 from which the primary cortex arises. 



Pericarp, -ium, the wall of an ovary that is developed 

 into a fruit. 



Perichastium, the sheathing structures in MuscinesB 

 which envelop the clusters of archegonia and an- 

 theridia. 



Peridium, the outer envelope investing the fructifi- 

 cation in certain Fungi. 



Perine, the outmost layer of sculpturing on the mem- 

 brane of pollen-grains. 



Perisperm, the tissue of the nucellus, in which, some- 

 times, food material is stored for the ultimate use 

 of the embryo. It is external to the embryo-sac. 

 In many old systematic books it is used for all 

 food- material of seeds which is external to the em- 

 bryo. 



Peristome, the ring of teeth around the mouth of a 

 Moss capsule. 



Perithecium, the flask-shaped cavity in which asci 

 are produced in certain Fungi. 



Petal, a corolla-leaf. 



Petaloid, -ine, like a petal. 



Petiole, the stalk of a leaf. 



*' Petit grain ", name for the ethereal oil yielded by 

 the leaves of the Orange-tree. 



Phaenology, that branch of botanical investigation 

 which deals wdth the recording, tabulation, and 

 comparison of the times and seasons at which plants 

 open their flowers and perform other periodic func- 

 tions in various portions of the globe. 



Phanerogamia, seed-bearing or flowering plants. 



Phloem, soft bast ; the soft outer portion of a vascular 

 bundle, of which sieve-tubes are the most charac- 

 teristic constituents. 



Phrygana, an old term for a growth of stiff and 

 prickly under-shrubs. 



Phycocyanin, the blue pigment of the Cyanophycese 

 or lowest Algae. 



Phycophaein, the brown pigment of the Brown 

 Algffi. 



Phycoerythrin, the purple colouring-matter of Red 

 Sea-weeds. 



Phylloclade, a branch assuming form and function 

 of a foliage-leaf: same as cladode. 



Phyllode, a petiole assuming the form and function 

 of a leaf -blade. 



Phyllotaxis, leaf-arrangement ; the arrangement or 

 order of distribution of leaves on the stem. 



Phylogeny, or Phylogenesis, the history of the 

 genealogical development of an organized being ; 

 the race history of an animal or plant, as distin- 

 guished from ontogeny, the history of individual 

 development. 



Phylum, a main division of the vegetable kingdom. 



Pileus, the cap-shaped receptacle of a Basidiomyce- 

 tous Fungus ; the umbrella-like part of a mushroom. 



Pili fasciculati, tufted hairs. 



Pili stellati, stellate hairs. 



Pinnate, when leaflets are arranged on either side of 

 a common rachis or petiole. 



Pistil, the female organ of a flower, consisting of 

 ovary (style) and stigma ; if the carpels are apocar- 

 pous there are many pistils ; if syncarpous, only 

 one. 



Pistillate, said of a plant or flower containing a 

 pistu ; most correctly, of one having no stamens. 



Pitcher, a tubular or excavated leaf, usually contain- 

 ing a liquid ; an ascidium. 



Pith, the central cellular part of a stem or root. 



Pits, thin places or depressions on cell- walls. 



Placenta, the part of the carpel which bears the 

 ovules; in Vascular Cryptogams, the portion of leaf- 

 surface bearing the sporangia. 



Plaited, folded; folded into plaits lengthwise ; jjlicate. 



Plant-formation, a term used to indicate the jire- 

 sence of two or more types of plant-community in- 

 termingled together, often in obvious strata. Cf. 

 vol. Ü. p. 896. 



Plasmodium, in the Myxomycetes ; a mass of naked 

 multi-nucleate protoi^lasm exhibiting amoeboid 

 movements. 



Pleomorphism, the occurrence of more than one 

 independent form in the life-cycle of a species, 

 especially in Fungi and Bacteria. 



Pleurocarpous, used of Mosses in which the arche- 

 gonia are borne, not at the tips of the main but of 

 secondary shoots. 



Plicate, of aestivation ; folded lengthwise in plaits. 



Plumule, the rudimentary shoot of an embryo. 



Pod. See Legume. 



Podium, a term for the torus or floral receptacle. 



Polar nuclei, the two nuclei — one from each end of 

 the embryo-sac of Angiosperms — which approach 

 one another and fuse to form the definitive nucleus 

 of the embryo-sac. 



Pollarding, the act of removing the crown of a tree 

 so as to induce it to throw out branches around the 

 place of amputation. 



Pollen, the mass of fecundating cells or grains con- 

 tained in the anther. 



Pollen-grain, one of the fecundating cells of the 

 pollen ; the microspore in flowering plants. 



Pollen-sac, the sporangium in which the microspores 

 or pollen-grains of flowering plants are developed. 



Pollen-tube, the tubular outgrowth of a pollen-grain 

 by means of which fertilization is achieved. 



Pollinia, masses of coherent pollen-grains. 



Polycarpellary, having or consisting of a number of 

 carpels. 



Polychotomous, branching repeatedly into equiva- 

 lent portions. 



Polyembryony, the production of more than a single 

 embryo in an ovule. 



Polyhedra, angular bodies which arise from the 

 zoospores into which the zygote of Hydrodictyon 

 breaks up. Ordinary Hydrodictyon-nets arise in- 

 side them. 



Porogamic, used of flowering plants in which the 

 pollen-tube effects an entrance to the ovule by the 

 microf)yle. 



Porous, used of dehiscence of anthers, &c., by means 

 of holes. 



Prickle, a sharp-pointed process of the epidermis or 

 cortex, but destitute of vascvdar tissue. 



Primordial utricle, that portion of the cell-protoplasm 

 which forms a bag in contact with the cell-wall. 

 An old name which has persisted in the terminology. 



Procumbent, lying along the ground. 



Prolepsis, something of the nature of an anticipation. 

 See vol. i. p. 8. 



Pro-mycelium, the limited tubular growth arising 

 from the chlamydospores in Hemibasidü and Uredi- 

 nese, from which conidia are abstricted. 



Prostrate, lying flat on the ground. 



