Knight — 104 — Dictionary 



Northocline. — A hybrid cline; an extension of the term cline 

 (q.v.) to cover the gradation of forms which occur in nature 

 following inter-specific hybridization. 



Nucellar Embryony. — The purely vegetative development of 

 cells in the nucellus or integument into the embryo sporophyte 

 (Darlington). The supernumerary embryos in Citrus are 

 formed in this way. See under Reproduction. 



Nuclear Budding. — The division of a nucleus into daughter 

 nuclei by constriction. 



Nuclear Disc. — The star-like group of chromosomes on the 

 equatorial plate at metaphase. 



Nuclear Division. — See under Mitosis, Meiosis and Amitosis. 



Nuclear Membrane. — The membrane surrounding the nucleus, 

 dividing the nucleoplasm from the cytoplasm. 



Nuclear Plate. — The equatorial plate. 



Nuclear Sap. — The more fluid ground substance of the 

 nucleus. 



Nuclear Spindle. — See under Spindle Elements and Spindle 

 Fibres. 



Nuclear System of Heredity. — The normal, mendelian, sys- 

 tem in which inheritance is controlled by genes located on the 

 chromosomes, as opposed to the corpuscular (= plastid) sys- 

 tem (q.v.) and the cytoplasmic (= molecular) system, q.v. 



Nucleocentrosome. — An intra-nuclear division centre simu- 

 lating a nucleolus, especially in Protista (Wilson). 



Nucleochylema. — Nuclear sap, q.v. 



Nucleohyaloplasm. — Nuclear sap, q.v. 



Nucleolar Organiser. — A specific chromomere responsible 

 for developing the nucleolus (McClintock; Darlington). 



Nucleolinus. — A deeply staining granule within the nucleolus. 



Nucleolus. — A darkly staining body occurring in the nuclei 

 of most cells. 



Nucleome. — The nuclear material of a single cell. 



Nucleomicrosomes. — Nuclear chromatin granules. 



Nucleoplasm. — The denser protoplasm of which nuclei are 

 composed as distinct from the less dense cytoplasm outside 

 the nuclear membrane. 



Nucleoplasmic Ratio. — The volumetric ratio of nucleus to 

 cytoplasm. 



Nucleoprotein. — A special protein in cell nuclei thought by 

 some to be the principal constituent of chromosomes (others 

 hold chromosomin to be the principal constituent). 



