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 seyeral 

 small clusters. 



Ohconical, inversely conical. 



Ollong, longer than broad. 



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

 than the lower.- 



Oltuse, rounded at the top. 



Orbicular, circular, spherical. 



Orifice, au 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, a membrane surrounding a spore. 



Pinna, a primary branchlet or leaflet. 



Pinnate, having only primary branchlets or pinnse springing 

 from either side. 



