362 INTRODUCTION TO BOTANY 
Monecious (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 stage of plants. A moncecious seed 
plant bears both staminate and pistillate flowers. 
Monopodial (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 hyphe. 
Naked. Wanting some usual covering. 
Nascent. Developing or growing. 
WNastic movements. Movements produced by all-round stimuli, as 
heat. The opening and closing of the flowers of crocuses and tulips 
are thermonastic 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 differing from the rest of the protoplasm 
in its greater density. 
Odgonium; pl. oogonia. The female reproductive organ of thallophytes. 
Odsphere (egg sphere). The egg cell; the mass of protoplasm pre- 
pared for fertilization. 
Odspore (egg spore). The egg cell after fertilization. 
Open bundle. A fibrovascular bundle which contains cambium. 
Operculum (a cover or lid); pl. 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. 
