APPENDIX 627 



which now shows a markedly bipolar structure, the young plant con- 

 sisting of only the leaf and root, whose tissues are perfectly continuous. 

 At this stage, absolutely no trace of any stem-structure is present. 



In O. pendulum the hypobasal part of the embryo, as in O. Moluc- 

 canum, gives rise to the large foot ; but the epibasal portion, instead of 

 developing into the cotyledon either at once grows out into a 

 single root, or, after a vertical division, each half may form an in- 

 dependent root. These roots (or root) grow for a long time, 

 and may branch without any evidence of a leaf being seen. The 

 development of the leafy shoot is not known, but it is highly probable 

 that the first leaf arises from an endogenous bud upon the root. 

 Bruchmann (5) has studied the embryo in O. vulgatufn, but was 

 unable to find the youngest stages. It resembles more nearly that of 

 O. pendulum, than O. Moluccanum, in the early development of the 

 root, which makes up the greater part of the embryo before any trace 

 of a leaf or stem-apex can be recognized. The stem-apex, according 

 to Bruchmann, arises near the base of the root, and is of superficial 

 origin ; but his figures suggest the possibility of an endogenous origin 

 similar to that of O. Moluccanum. In O. vidgatum the first leaves are 

 rudimentary, and remain permanently underground. It is several 

 years (8-10 according to Bruchmann) before the first green leaf 

 appears above ground. 



In O. Moluccanum, at the time the first leaf is completely developed, 

 the young sporophyte consists simply of this leaf, whose lamina shows 

 the characteristic netted venation of the older plant and the root. 

 The slender petiole is continued directly into the root, it being im- 

 possible to determine where the petiole ends and the root begins. 



In the stele of the leaf the single protoxylem arises on one side, and 

 the butndle at maturity has the ^'collateral form." The single xylem 

 of the leaf-stele is continued into the root as the single xylem of its 

 ''monarch" bundle. 



Mettenius's account of the development of the embryo in 0. 

 pedunculosum agrees closely with the writer's studies on O. Molucca- 

 num. Mettenius describes the origin of the stem-apex as a bud 

 upon the root, but did not investigate its exact origin, but it no doubt 

 is the same as in O. Moluccanum. 



In the latter the first evidence of the permanent growing-point of the 

 sporophyte is the formation of a group of meristematic cells close to 

 the stele of the root, very much, indeed, like the origin of a secondary 

 root. From this meristem there are differentiated a leaf and the 

 stem-apex, apparently quite independently of each other. The 



