EXPLANATION OF TERMS. 



485 



logically as an axis which maybe branched 

 or unbranched. 



Pileus. In Hymenomycetes : cap-like 

 summit of a ' fructification ' bearing the 

 hymenium. 



Pitcher. A tubular expansion backwards 

 of a portion of a leaf-lamina forming a 

 trap for the capture of insects which are 

 digested by the agency of a pepsin ferment 

 secreted within the pitcher. 



Placenta. In vascular Cryptogams and 

 Phanerogams : the tissue from which 

 sporangia arise. 



Placentation. Disposition of the placenta. 



Planogamete. Motile gamete. Same as 

 zoogamete. 



Plasmodiuni. In Myxomycetes : body of 

 naked multinucleated protoplasm ex- 

 hibiting amoeboid movements. 



Plerome. Axile meristematic portion of 

 a growing point surrounded by the 

 periblem. 



Plerome sheath. Same as bundle sheath. 



Pleurocarpous. In Musci : forms are 

 pleurocarpous when archegonia (within 

 which the sporocarp or ' Moss-fruit' is 

 developed) are borne at the extremity 

 of a leafy axis of the second or third 

 order and the growth of the primary 

 axis is thus unlimited. Comp. acrocar- 

 pous. 



Plumule. Primary leaf-bud of an embryo. 



Pluricellular. Composed of two or more 

 cells. 



Plurilocular. Having two or more loculi. 



Polar-nucleus. The fourth nucleus in 

 each group at the two extremities of the 

 embryo-sac which move towards the 

 middle of the embryo-sac and there 

 coalesce to form the secondary nucleus 

 of the embryo-sac. 



Pollen- chamber. In Cycads : cavity at 

 apex of ovule beneath the integuments 

 in which the pollen-grains (microspores) 

 lie after pollination. 



Pollen-grain. Microsporein Phanerogams. 



Pollen-sac. Microsporangium in Phaner- 

 ogams. 



Pollination. Dusting of receptive surface 

 of female organ with pollen-grains. 



Pollinium. Body composed of all the 

 pollen-grains of an anther-loculus. 



Pollinodium. In Ascomycetes : term for 

 male sexual organ which either directly 

 or by means of an outgrowth conjugates 

 with the female sexual organ. 



Polycarpellary. Composed of two or more 

 carpels free or united. Comp. mono- 

 carpellary. 



Polycarpic. A plant producing fruit more 

 than once in course of its life is poly- 

 carpic. Comp. monocarpic. 



Polycarpous. A flower in which the 



gynaeceum forms two or more distinct 

 ovaries is polycarpous. Comp. mono- 

 carpous. 



Polyembryony. In Phanerogams : pro- 

 duction of more than one embryo within 

 an ovule. 



Polygamous. Having hermaphrodite and 

 unisexual flowers on the same or on 

 different individuals of a species. 



Polyhedra. In Hydrodictyon : special 

 angular cells with horn-like processes 

 formed by the swarm-cells produced in 

 the zygospore and within each of which 

 a new coenobium is developed. 



Polymerous. An ovary formed of two or 

 more carpels united together is poly- 

 merous. Comp. monomerous. 



Polypetalous. Having free petals. Same 

 as choripetalous. Comp. garnopeta- 

 lous. 



Polysepalous. Having free sepals. Same as 

 chorisepalous. Comp. gamosepalous. 



Polyspermous. Having two or more 

 seeds. Comp. monospermous. 



Polysymmetrical. Same as actinomor- 

 phous. 



Pore-capsule. Capsule dehiscing by pores. 



Posterior. Of flower or other lateral 

 member : side next the parent axis is 

 posterior. Camp, anterior. 



Primary cortex. Same as periblem. 



Primary tapetal cell or layer. In 

 Eusporangiatae : the cell or layer from 

 which by division the tapetum is derived. 

 It is formed by bipartition of a cell or 

 layer of periblem, the other product 

 being the archesporium. 



Primine. Outer integument of an ovule 

 when two are present. 



Primordial utricle. Layer of protoplasm 

 lining the inner surface of the wall of a 

 vacuolated cell. 



Primordium. First beginning of any 

 structure. 



Procarp. In Rhodophyceae and Asco- 

 mycetes : a unicellular or pluricellular 

 female sexual organ consisting of a 

 receptive apparatus, trichogyne, (and in 

 the most complex forms of a transmitting 

 apparatus, trichophore), and of a portion, 

 carpogonium, in which the protoplasm 

 is not rounded off to form an oosphere 

 and which is excited by fertilisation to a 

 process of growth resulting in a sporocarp. 



Proembryo. (a) In Characeae : product of 

 development and division of oospore upon 

 which the characeous plant developes as 

 a lateral bud. (b) In Archegoniatae : 

 product of development and division of 

 oospore before differentiation of embryo. 



Proembryonic branch. In Chara : pro- 

 pagative body with structure of proembryo 

 springing from a node of the stem. 



