EXPLANATION OF SCIENTIFIC TERMS. 303 



Nucleoli, a small cluster of spores forming part of a nu- 

 cleus. 



Nucleus, a mass of spores sometimes composed of several 

 small clusters. 



Obconical, inversely conical. 



Oolong, longer than broad. 



Obovate, about twice as long as broad, the upper end larger 

 than the lower. 



Obtuse, rounded at the top. 



Orbicular, circular, spherical. 



Orifice, an opening. 



Oscillate, to move to and fro like a pendulum. 



Ovate, egg-shaped, about twice as long as broad, the lower 

 end larger than the upper. 



Palmate, hand-shaped. 



Paranemata, filaments that accompany spores. 



Parasitic, growing upon other plants, and deriving nourish- 

 ment from them. This word is improperly applied to 

 sea-weeds, as they do not derive nourishment through 

 their roots. They should be said to be epiphytic. 



Patent, spreading. 



Pectinate, set with comb-like branches or branchlets. 



Pedicellate, stalked. 



Pellucid, transparent. 



Pendulous, drooping, hanging. 



Perennial, lasting more than two years. 



Perforate, pierced with small holes. 



Pericarp, a spore vessel or its walls. 



Periderm, a membrane surrounding a spore cluster. 



Periphery, the outer layer of cells of a cylindrical frond. 



Peripheric, belonging to the periphery. 



Perispore, sl membrane surrounding a spore. 



Pinna, a primary branchlet or leaflet. 



Pinnate, having only primary branchlets or pinnae springing 

 from either side. 



