ANGIOSTERMS: SEED. 333 



within the ovule and the growth of the endosperm is taking 

 place, where this is formed, other correlated changes occur in 

 the outer parts of the ovule, and often in adjacent parts of the 

 flower. These unite in making the " seed, " or the " fruit. " 

 Especially in connection with the formation of the seed a new 

 growth of the outer coat, or integument, of the ovule occurs, 

 forming the outer coat of the seed, known as the testa, while 

 the inner integument is absorbed. In some cases the inner 

 integument of the ovule also forms a new growth, making an 

 inner coat of the seed (rosaceae). In still other cases neither 

 of the integuments develops into a testa, and the embryo sac 

 lies in contact with the wall of the ovary. Again an additional 

 envelope grows up around the seed; an example of this is 

 found in the case of the red berries of the " yew " (taxus), the 

 red outer coat being an extra growth, called an aril. 



In the willow and the milkweed an aril is developed in the 

 form of a tuft of hairs. (In the willow it is an outgrowth of 

 the funicle, = stalk of the ovule, and is called a funicular aril; 

 while in the milkweed it is an outgrowth of the micropyle, = 

 the open end of the ovule, and is called a micropylar aril.) 



664. Increase in size during seed formation. Accompany- 

 ing this extra growth of the different parts of the ovule in the 

 formation of the seed is an increase in the size, so that the seed 

 is often much greater in size than the ovule at the time of fer- 

 tilization. At the same time parts of the ovary, and in many 

 plants, the adherent parts of the floral envelopes, as in the apple; 

 or of the receptacle, as in the strawberry; or in the involucre, 

 as in the acorn ; are also stimulated to additional growth, and 

 assist in making the fruit. 



