GLOSSARY. 179 



Indusium, pi. indusia (clothing). In ferns, a cellular outgrowth 

 of the leaf covering the clusters of sporangia (sori). 



Inflorescence (flowering). The arrangement of flowers; or the 

 flowering portion of a plant. 



Integument (covering). The covering of the ovule. 



Intercellular. Between or among the cells. 



Internode. The part of a stem between two nodes. 



Intine (on the inside). The inner coat of a pollen-spore. 



Involucre (rolled within). The leaf-like or bracteate set of 

 organs that incloses a cluster of flowers. 



Isogamous (equal gametes). Applied to those plants whose 

 pairing gametes are similar. 



Lamina (a layer). The blade, or expanded part, of a 

 leaf. 



Leaf-trace. The fibro-vascular bundles from the leaf which 

 descend into the stem, and sooner or later become blended 

 with its fibro-vascular system. 



Leptosporangiate (slender- vesseled). Applied to those plants 

 whose sporangia arise from one superficial cell. 



Ligule (a small tongue). In grasses, a thin appendage at the 

 junction of leaf-blade and sheath. 



Lodicule (a small coverlet). A small scale in the flower of 

 grasses. 



Medullary (belonging to the marrow). Relating to the pith; 

 medullary rays are the pith-rays which pass outward to 

 the bark between the fibro-vascular bundles. 



Megaspore, or Macrospore (great or large spore). The larger 

 one of the two kinds of asexual spores produced by certain 

 Pteridophytes and all Spermatophytes. 



Megasporangium (large spore- vessel). The sporangium that 

 produces the megaspores. 



Megasporophyll (large spore-leaf). The leaf upon which the 

 megasporangium develops. 



Meristem (dividing tissue) . Tissues in a nascent or differentiat- 

 ing state. 



Mesophyll (middle leaf). The green or soft tissue of a leaf, 

 supported by the framework and exclusive of the epider- 

 mis, called by the older botanists parenchyma. 



Micropyle (small gate). The opening left by the integuments 

 of the ovule, and which leads to the nucellus. 



Microsporangium (small spore- vessel) . The sporangium that 

 produces the microspore. 



