204 Explanation of Terms. 



Immunity. — -The absence of susceptibility to an infectious disease, even although the 



germ-tube of the parasitic fungus has entered the host-plant, without, however, 



multiplying therein and producing disease. 

 Incicbation-period. — -The time which elapses between the introduction of the infective tube 



and the production of the characteristic fungus. 

 Indigeyious. — Native to a country and not introduced, at least within the historic period. 

 Infection. — The introduction of a living micro-organism or the germ-tube of a parasitic 



fungus into the host-plant, where it multiplies and produces disease. 

 In florescence. ^The arrangement of several flowers on a common axis, and in grasses the 



axis or stalk is known as the Rachis. 

 Inoculation. — The entrance of the germ-tube of the parasitic organism into the host- 

 plant, irrespective of the causation of disease. 

 Intercellular. — Between the cells of the host-]ilant. 

 Intracellular. — -Within the cells of the h(ist-i)lant. 



Lumen. — The cavity bounded by the walls of an organ, as the central cavity of a cell. 

 Jletabolism. — -The sum of the chemical changes in a living cell. 

 Micron or Micromillimctre. — -The standard unit for microscopical measurements equalling 



1-lOOOth of a millimetre, or 1 -25000th of an inch, and indicated by the sign ^{. 

 Mycelium. — The vegetative portion of a fungus composed of hyphae. 

 Nucleus. — An organized prote'l constituent of the cell, playing an important part in its 



nutritive and reproductive processes. 

 Oospore. — -The fertilised cvum or egg-cell. 



Ooary. — ^That portion of the female organ of a flowering plant which contains the ovules. 

 Parasite. — An organism living on or in another living organism and at its expense. 

 Pathology. — The science of disease. Vegetable Pathology is that division of it which 



treats of plant diseases. 

 Peridium. — The enveloping layer enclosing spores as -in the Puff-balls and the aecidium 



of the Rusts. 

 Phycomycetes. — A group of fungi which are alga-like in their characters, with sexual and 



asexual reproduction. 

 Predisposition. — The tendency to disease exhibited by an organism when the conditions 



are favorable to the development of the parasite. 

 Promycdium.. — Applied to the germinal tube produced by the spore of the Rusts and Smuts. 

 Pronucleus. — The nucleus of a conjugating gamete which unites with another pronucleus 



to form the germ-nucleus. 

 Protdbasidium. — -A basidium transversely divided and consisting of several cells. 

 Protoplasm. — -The living substance of which animals and plants are composed. 

 Pseudomixis.— The union of the sexual cells in the process of conjugation, when they are 



approximately equal. 

 Pulverulent. — Powdery, applied to spores when they are dusty and not agglutinated 



together. 

 Rachis. — -The axis or stalk in the inflorescence of grasses. 

 Recessive. — -Applied to such contrasted characters, arising in the crossing of two 



individuals, as are kept in abeyance or apparently suppressed, at least, in the 



first generation. 

 Saprophyte. — A fungus which preys upon dead organic matter only, in contrast to a 



(Septofe.— Partitioned off into distinct divisions. 



Septum. — A partition or cross- wall. 



•Sorus. — A cluster of spores constituting a spore-bed. 



Spore.— A detachable cell capable of reproducing the fungus. 



Sporidium. — A spore abjointed from a promycelium, equivalent to a conidium. 



Sporidiolum is the term proposed by Saccardo, since sporidium is already applied 



to an ascospore. 

 Sporophyte. — The stage in the life-cycle of a plant which bears the spores. 

 Stigma. — The top of the pistil upon which the pollen is received. 



Stroma.— Fundus body in the form of a cushion or expansion, bearing reproductive bodies. 

 Symbiosis. — -The living together of dissimilar organisms which mutually help and support 



each other. 

 Teleutospore. — Generally regarded as the ultimate spore in the life-cycle of the Riists 



which germinates and produces a promycelium. Sometimes also applied to the 



spore of the Smuts. 

 Toxin.^A poisonous secretion of certain Fungi which kills the cells of the host-plant and 



^prepares the way for the entrance of the parasite. 

 Unicellidar. — -Consisting of a single cell. 

 Uredospore. — A spore detached from the apex of a pedicel and producing a mycelium which 



bears uredospores or teleutospores or both. 

 Vacuole. — A space in the protoplasm of cells which contains a watery fluid, the cell-sap. 

 Verrucose. — Warty, covered with small warts. 



