EXPLANATION OF TERMS. 



489 



Teeth. General term for any short pointed 

 marginal lobe. In Musci : applied to the 

 delicate processes, formed of portions of 

 cell-membrane, surrounding the mouth of 

 the capsule after removal of the oper- 

 culum. 



Teleutospore. In Uredineae : gonidium 

 formed by abjunction on, but not separa- 

 ting from, a sterigma, and on germination 

 producing a promycelium. 



Tetracyclic. A flower with four whorls 

 of members is tetracyclic. 



Tetradynamous. An androecium in which 

 there are four long and two short stamens 

 is tetradynamous. 



Tetragonidium. In Rhodophyceae: one 

 of the gonidia formed by division into 

 four parts of a mother-cell. 



Tetramerous. A flower in which calyx, 

 corolla, and androecium have eachfour (or 

 a multiple of four) members, is tetra- 

 merous. 



Thalloid. Hepaticae in which the vegeta- 

 tive body is not a leafy stem are termed 

 thalloid. 



Thallus. A vegetative body without dif- 

 ferentiation into stem and leaf. 



Theca. Used in the same general sense 

 as capsule. In this book applied espe- 

 cially to the capsule in Musci. 



Theoretical diagram. A floral diagram, 

 not representing what may be found at 

 once by examination of a flower, but 

 containing indications of circumstances 

 suggested by purely theoretical considera- 

 tions. 



Torus. Portion of floral axis on which 

 the leaves of a flower are inserted. 



Trabecula. In Ligulatae : sterile row 

 or plate of cells with intercellular spaces 

 crossing the cavity of a sporangium. 



Trama. In Hymenomycetes : hyphal 

 tissue in middle of lamella on pileus. 



Transversal wall. In Archegoniatae : 

 wall cutting the basal wall and the 

 median wall in a proembryo at right 

 angles, and separating an upper from a 

 lower half. 



Trichogyne. Thread-like receptive portion 



of a procarp. 

 Trichophore. In Rhodophyceae : row of 



cells of procarp bearing the trichogyne. 

 Trimorphism. In flower : heterogony 

 with three forms, the long-styled, the 

 mid-styled, and the short-styled flower. 

 See dimorphism. 



Tryma. Inferior drupe in which the meso- 

 carp and epicarp separate from the hard 

 endocarp as in Juglans. 

 Tuber. Thickened underground branch, 

 globular or ovoid in form without a 

 coating of scale leaves and bearing leaf 

 buds. 



Typical diagram. When comparison of 

 a number of empirically different dia- 

 grams yields the same theoretical dia- 

 gram, this is termed a type or typical 

 diagram. 



Umbel. Simple racemose monopodial in- 

 florescence with primary axis contracted 

 in the region of branching and flowers 

 pedicellate. 



Umbellule. An ultimate umbel in a com- 

 pound umbel. 



Uniaxial. When the primary stem of a 

 plant does not branch and ends in a 

 flower, the plant is uniaxial. 



Unilocular. Having one cavity or lo- 

 culus. 



Uniparous cyme. Cymose branching in 

 which only one member is produced at 

 each branching. 



Unisexual. Having only one kind of 

 sexual organ. 



Uredospore. In Uredineae : gonidium 

 formed by acrogenous abjunction on a 

 sterigma from which it separates when 

 mature, and on germination produces a 

 mycelium bearing uredospores and teleu- 

 tospores. 



Urn. In Musci : same as theca and 

 capsule. 



Vaginula. In Musci : apex of the stem 

 which sheaths round the embedded foot 

 of the sporogonium. 



Vallecular canal. In Equisetaceae: inter- 

 cellular canal in the .cortical parenchyma 

 and opposite a groove on the surface 

 of the stem. 



Valve, (a) In Diatomaceae : each half of 

 the silicified membrane is a valve, (b) 

 In Phanerogams: a portion which is sepa- 

 rated off or raised like a valve in dehis- 

 cence of anthers and fruits. 



Velum. In Isoetes : out-grown mem- 

 branous margin of the fovea of leaf cover- 

 ing over the sporangium ; is also termed 

 indusium. 



Velum partiale. In Hymenomycetes: a 

 veil of varying texture stretching across 

 from the stipe to the margin of the pileus 

 and covering the hymenium. 



Velum universale. In Hymenomycetes : 

 a membrane or wrapper enclosing the 

 whole developing 'fructification.' Same 

 as volva. 



Venter. Expanded basal portion of arche- 

 gonium in which oosphere is formed. 



Ventral canal-cell. Small cell in arche- 

 gonium cut off from mother-cell of 

 oosphere below the entrance of neck. 



Versatile. Swinging freely on a support. 



Volva. Same as velum universale. 



