GLOSSARY 527 



' Monoecious (one household). Applied to those plants upon one of 

 which both kinds of gametes are borne. Strictly speaking, the term 

 applies only to the gametophyte sta^e of plants. A monreeious seed 

 plant bears both staminate and pistillate flowers. 



Monopodlal (having one foot). Said of a stem consisting of a single 

 and continuous axis (footstalk). 



Mother cell. A cell that produces new cells (usually) by internal 

 division. 



Mutualism. A symbiotic relationship in which the organisms are 

 mutually helpful. 



Mycelium (fungous growth). The filamentous vegetative growth of 

 fungi, composed of hyphae. 



Naked. \Vanting some usual covering. 



Nascent. Developing or growing. 



Nastic movements. Movements produced by all-round stimuli, as 

 heat. The opening and closing - of the flowers of crocuses and tulips 

 are thermonastio movements. 



Nectary. The structure in which nectar is secreted. 



Nerve. A simple vein or rib. 



Node (a joint). That part of a stem which normally bears leaves. 

 ^Nucellus (a little kernel). The mass of the ovule within the in- 

 teguments. 



Nucleolus (diminutive of nucleus). The sharply defined rounded part 

 often seen in the nucleus. 



Nucleus (a kernel). The usually roundish mass found in the proto- 

 plasm of most active cells, and difiering from the rest of the protoplasm 

 in its greater density. 



Oogonium; pi. obgonia. The female reproductive organ of thallophytes. 



Oosphere (egg sphere). The egg cell; the mass of protoplasm pre- 

 pared for fertilization. 



Oospore (egg spore). The egg cell after fertilization. 



Open bundle. A fibrovascular bundle which contains cambium. 



Operculum (a cover or lid) ; pi. opercula. In mosses the terminal lid 

 of the capsule, just beneath the calyptra. 



Osmosis. The interchange of liquids through a membrane. 



Ovary (egg-keeper). That part of the carpel in which the ovules 

 are formed. 



Ovule (an egg). The body which becomes a seed after fertilization 

 and maturation ; formerly thought to be an egg. 



Palet (chaff). In grasses, the inner bract of the flower. 



Palisade cells. The elongated parenchyma cells of a leaf, which 

 stand at right angles to its surface and are often confined to the upper 

 part of the leaf. 



