IN CEYLON. 61 



ovalif ojiajhere is no splitting of the testa, and it is impossible 

 for an expanded cotyledon to effect its exit from such a 

 small circular micropylar opening amply filled by the 

 thin axis of the hypocotyl : in other species there is only a 

 partial splitting, and even in calamander seeds the gap is 

 never large enough to allow the cotyledons to escape 

 intact. 



Since the splitting of the testa would be more complete if 

 the endosperm were exhausted more quickly, it follows that 

 probably all the forces mentioned above play some part in the 

 final detachment of the cotyledons. 



The mode of development just described is not a conse- 

 quence of the artificial raising of the seeds ; the detachment 

 occurs in nature, and the internal characters of the epicoty- 

 ledonary and cotyledonary traces indicate that this line 

 of development has been habitual for a considerable period 

 of time. This mode of development is characteristic of some 

 of our rarest species, and is probably one of the factors which 

 is leading to the extinction of many species. 



The detachment of the cotyledons is attended with the 

 minimum disadvantages in those species having short hypo- 

 cotyls Q). insignisand D. Embry_pteris). In these instances 

 the seed coat, endosperm, and cotyledons are but rarely 

 raised above the surface of the soil, and the young though 

 enhanced epicotyledonary parts, gain easy exit. 



The habit of D. insignis in particular is very suggestive of 

 a hypogeal tendency, since the seeds are rarely raised above 

 ground, the hypocotyl is very short, and the epicotyl stem 

 very long and provided with small leaf rudiments suggestive 

 of typical Garcinia seedlings. 



The morphological relationships of the parts of the seed- 

 lings are also of interest. In the first case it is worthy 

 of note that in those species possessing short hypocotyls the 

 epicotyledonary axis is usually long (4 to 1- cm.), whereas 

 in those having hypocotyls of normal length the epicotyle- 

 donary axis is usually only from O5 to 1*5 cm. in length. 



