766 



A TEXTBOOK OF THEORETICAL BOTANY 



The habit of the plant may be likened to an enormous woody carrot, the 

 top of which may be as much as 4 ft. across, though 2 ft. is the more normal 

 mature size. It rises about 18 in. above the ground and tapers sharply 



I 



Fig. 766. — Gnetum gnemon. Development of female gametophyte. A, Longitudinal 

 section of young ovule showing the deep-seated position of the embryo sac. 

 B, Embryo sac with parietal nuclei and well-developed nutritive " pavement " 

 tissue in the nucellus below the embryo sac. C, Mature embryo sac showing 

 prothallial tissue formed at the antipodal end. (A a7id B after Coulter, C after 

 Thonipsoti.) 



downwards into a tap root which descends to unknown depths in the sandy 

 soil. Across the top there is a deep furrow, running transversely to the leaves. 



There are only two leaves, enormous leathery structures, like green 

 straps, which lie on the ground and are usually more or less split into ribbons. 

 They are about 6 ft. long in old specimens and about i ft. across. They arise 

 from a pair of grooves, one on each side of the crown, which extend nearly 

 round its circumference, and they continue to grow from a basal meristem 

 during the whole life of the plant, which may last for a century. 



The plant is invariably dioecious, though it has been recorded that young 

 plants which have germinated close together may become so fused in growth 

 as to be mistaken for a single plant, which may sometimes give rise to an 

 appearance of bisexuality. 



The inflorescences are male and female strobili, borne on branching 

 stalks, arising from the rim of the crown, just above the leaf grooves. 



Seedlings have often been raised in cultivation, and their development 

 sheds light on the strange morphology of the adult plant. Germination is 

 epigeal, the two cotyledons being withdrawn from the seed and turned up 

 into the light. There is a short hypocotyl and a primary tap root. The seed 



