2 THE STORY OF PLANT LIFE 



parent plant, remains inactive in the soil, exhibiting 

 no living characteristics, until the external condi- 

 tions make for its entrance into the world of life. 



The embryo in this state is provided with endo- 

 sperm in most Monocotyledons, a large proportion 

 of which are aquatic, and usually herbaceous. 

 Amongst Dicotyledons, however, there are seeds with 

 endosperm, which are called albuminous, and those 

 without endosperm or exalbuminous. In the former 

 case the endosperm serves as reserve material upon 

 which the embryo can draw in the early stages of 

 germination before the cotyledons have become 

 functional, or before the first leaves have appeared. 

 Where there is no endosperm the cotyledons them- 

 selves are large and supply the necessary material 

 for setting in motion or starting into being the 

 activities of the young plantlet or embryo. 



In the seed the embryo is already differentiated, 

 with a radicle which develops into the root, on 

 germination, and one or two cotyledons according as 

 the plant is a Monocotyledon or a Dicotyledon, which 

 subtend or enclose a plumule or bud which gives rise 

 to the stem. Around these lies in albuminous seeds 

 the endosperm which may be mealy, oily, fleshy, or 

 horny. The seed-coat may consist of one coat or 

 two. In the latter case the inner coat is the 

 tegumen, the outer the testa. Sometimes an arillus 

 surrounds the latter, as in the Water Lily, or a 

 caruncle may be formed. 



The seeds may be large or small. The former are 



