186 NATURE TEACHING. 



Plastic. (Greek plastos, moulded.) Capable of being 

 moulded or worked into various shapes. For 

 instance, potters' clay is plastic. 



Plumule. (Latin, plumula, a little feather.) The 

 name given to the undeveloped shoot (that is the 

 stem bud), of the embryo. Its appearance in 

 such seeds as the bean probably suggested the 

 name. 



Pod. A dry (not fleshy) fruit, containing several 

 seeds, which usually splits .open when ripe -along 

 both sides. 



Pollen. (Latin, pollen, anything as fine as dust, hence 

 very fine flour.) The powdery substance con- 

 tained in the stamens, essential to the fertiliza- 

 tion of flowers. 



Pollination. The act of placing pollen on the 

 stigma of a flower. Usually, but not necessarily, 

 followed by the fertilization of the flower. In- 

 sects can pollinate flowers, but they cannot 

 fertilize them. 



Propagate. (Latin, propago, I propagate, I ex- 

 tend.) To increase the numbers of a plant by 

 means of cuttings, reproduction by seeds, or 

 other methods. 



Pungent. (Latin, punyo, I sting.) Used to des- 

 cribe the smell of such a substance as ammonia. 



Pupa. (Latin, pupa, a baby.) The third stage in the. 

 life of many insects, usually inactive. The name 

 was given from the resemblance of many to a 

 baby bound up in clothes as is the custom in 

 Southern Europe. Pupa and chrysalis refer to 

 the same condition. 



Radicle. (Latin, radix, a root ; hence radicle, a little 

 root.) The young root of the embryo. 



Respiration. (Latin, respiratio, the act of drawing 

 breath.) Used to denote the breathing process 

 in both plants and animals. 



Rudimentary. (Latin, rudimentum, a first attempt, 



