1494 A TEXTBOOK OF THEORETICAL BOTANY 



qiiadrangidaris) there is also a fleshy upgrowth from the funicle which 

 envelops the seed and grows beyond the micropyle. It forms part of the 

 edible flesh of the fruit, in the same way that the soft outer testa does in 

 Punica, the Pomegranate. 



Many species of Acacia have extraordinarily long funicles, which are 

 strikingly contorted and wind round the seeds (Fig. 1368). They become 

 dry and brightly coloured and remain attached to the seeds when they are 

 shed. They are not correctly described as arils but they are closely similar 

 and probably have a similar attraction for birds to that of some arils. 



i 



jf 



Fig. 1368. — Acacia melanoxylon. Seeds surrounded by the 

 orange arils which develop from the funicles. The seeds 

 hang from the open pods. 



We have previously mentioned that the endosperm in some ovules is 

 arrested during the development of the embryo and may entirely disappear 

 before the seed is ripe or may remain only as a thin membrane around the 

 mature embryo. Only in a few plants, particularly some of the Orchids, 

 is endosperm formation entirely suppressed, a reduction phenomenon 

 which is in line with the imperfect and arrested development of the embryo 

 in that family. Seeds in which the endosperm forms a visible mass are 

 known as "albuminous", an archaic term, for the endosperm may often 

 be wholly starchy. The endosperm is purely a reserve of nutriment for 

 the embryo and shows no capacity for development or diflFerentiation. 

 Almost the only exception to this is in Criniim (Amaryllidaceae), where the 

 endosperm develops a corky covering, supplying the place of the missmg 

 testa, and may also develop chlorophyll. 



