GLOSSARY AND INDEX. 281 



perennial, living an indefinite term of years, 52. 



perfoliate, applied to a leaf the basal part of which is so extended and 



united, around the stem that the latter appears to grow through it, 58. 

 perianth, the floral envelopes collectively. 

 pericarp, the modified wall of the ripened ovary, 10, 89, 92. 

 perichaetium, the circle of leaves surrounding the fructification of mosses, 



125. 

 perigynium, the sac enclosing the ovary of sedges, 162. 

 perisperm, tissue enclosed by the walls of the ovule, but lying outside of 



the embryo-sac, 84. 

 peristome, the circle of teeth surrounding the opening of the capsule of 



mosses, 124. 

 persistent, remaining attached, as leaves after the usual time of falling, 



or floral envelopes until the fruit is ripe, 153. 

 petal, one of the leaves of the corolla, 79. 

 petiole, the stalk of a leaf. 

 petiolate, having a petiole, 58. 

 phsenogamous or phanerogamous, flowering, producing true flowers and 



seeds, in distinction from cryptogamous or flowerless. These terms 



are retained for convenience, but the distinction is less sharply 



defined than was formerly supposed. 

 phaenogamic or phanerogamic, see phsenogamous. 

 phloem, that part of a vascular bundle characterized especially by the 



presence of sieve-tubes. Cambiform and companion cells and bast 



fibers are other elements of the phloem, but are not all necessarily 



present. 

 phyllode, an expanded petiole taking the place of a leaf-blade, as in 



many acacias. 

 phyllotaxis, leaf arrangement, 59, 68. 

 pinna (pi. ^imnce), one of the divisions of a pinnately compound leaf, or 



a primary division of a bipinnately or tripinnately compound leaf, 



131. 

 pinnate, feather-like, pinnately compound, 58. • 



pistil, the gynoecium, or part of the flower that produces ovules, 74, 79. 

 pistillate, having a pistil, or pistils, but no stamens, 85. 

 placenta (pi. placentce), the part of the ovary on which the ovules are 



borne, 76. 

 plasmolysis, contraction of the protoplasmic sac, followed by its separa- 

 tion from the cell-membrane in which it is enclosed, 101. 

 plumule, the part of the embryo above the insertion of the cotyledons or 



cotyledon, 2. 

 pollen, the fertilizing cells contained in the anther, 77. 



