438 PLANT MORPHOLOGY 



Mitosis. The series of complex changes through which a nucleus ordinarily passes 

 when it divides. 



Monocotyledonous. Having a single cotyledon. 



Monoecious. Having the male and female organs on the same plant; having stamens 

 and pistils in separate flowers on the same plant. 



Monophylletic. Developed from a single stock or from a common ancestry. 



Monopodium. A main stem that continues its original line of growth, giving off lat- 

 eral branches. 



Monosiphonous. Consisting of a single filament. 



Monosporangiate. With microsporangia and megasporangia borne in separate 

 strobili or flowers. 



Multicellular. Many-celled. 



Multiciliate. Having many cilia. 



Multilocular. Having many locules or cavities. 



Mycelium. The mass of hyphae forming the vegetative body of most fungi. 



Myxamoeba. A uninucleate, amoeboid, reproductive cell in the myxomycetes. 



Naked flower. A flower without a perianth. 



Nucellus. The main body of an ovule, constituting the megasporangium, and sur- 

 rounded by the integument or integuments. 



Nucleus. A rounded protoplasmic body, enclosed by a membrane, embedded in the 

 cytoplasm of nearly all cells, and controlling their metabolism, growth, reproduc- 

 tion, and inheritance. 



Ontogeny. The development of an individual organism throughout its successive 



growth stages. 

 Oogonium. The female sex organ of thallophytes. 

 Operculum. A lid formed at the top of a capsule, as in mosses. 

 Orbicular. Flat and circular, or nearly circular, in outline; disk-shaped. 

 Orthotropous. Having the ovule erect, with the micropyle and chalaza at opposite 



ends. 

 Ovary. In angiosperms, the part of the pistil that contains the ovules. 

 Ovule. The megasporangium of a seed plant with its integument or integuments; an 



immature seed. 



Palisade tissue. The portion of the mesophyll that is composed of elongated cells 



lying directly below and at right angles to the upper epidermis of a leaf. 

 Palmate. Having lobes, divisions, or leaflets radiating from a common center. 

 Papilla. A small protuberance or projection. 

 Paramylon. A starch-like carbohydrate constituting a form of reserve food in the 



Euglenophyceae. 

 Paraphysis. One of the sterile filaments commonly accompanying the sporangia or 



gametangia in many thallophytes and bryophytes. 

 Parasite. An organism living on or in another organism and getting its food at the 



other's expense. 

 Parenchyma. A soft, loose tissue composed of living, thin-walled cells that are not 



greatly differentiated. 

 Parietal. Pertaining or belonging to the walls of a part or cavity. 

 Parthenocarpy. The development of a fruit without fertilization. 

 Parthenogenesis. The development of an embryo from an unfertilized egg. 

 Pellicle. A thin, firm, outer membrane on certain unicellular organisms that lack a 



cell wall, such as Euglena. 



