EMBRYOLOGY 



467 



early formation of the root, and late development of the axis and leaf: 

 in the second, leaf and root only are developed, in the third roots only : 

 the definitive sporophyte in both O. moluccanum and pendulum is 

 '" formed as an adventitious bud upon the root of the embryo sporophyte." 

 It would thus appear that the genus Ophioglossum shows almost equal 

 variety in its embryogeny to that seen in Lytopodium. It has been seen 







FIG. 260 bis. 



Ophioglossum vulgatum, L. 58 = 

 longitudinal section through a young 

 seedling. <w = first root with evident 

 apical cell; /=the foot only slightly 

 projecting; t' = the epibasal region of 

 the embryo ; p = rudiment of pro- 

 thallus. X35. 61 = larger, three- 

 rooted seedling in longitudinal section ; 

 /> = prothallus ; 'i = first root; h 

 entering fungal filament; = endo- 

 pnytic fungus. zi> = insertion of and 

 and 3rd roots; s^apex of rhizome: 

 b\, b%, &j = leaves; c, c = canal ; hl\- 

 hl\ = sheath of first leaf; hl. r hL = sheath 

 of second leaf; /z/ 3 = sheath of third 

 leaf, x 35. (After Urucbmann.) 



in that genus how the different forms are referable to variation of a single 

 type, and it seems probable that the same should be the case also for 

 the embryos of Ophioglossum. In Lycopodium the variants arise through 

 tuberous swellings and delay of root-formation : here the variants arise in 

 relation to the precocity of the root, a feature related in all probability 

 to mycorhizic nutrition. We have seen that the development of the axis 

 is delayed in O. vulgatum, which may be held to be a less specialised 

 type, though still with precocious root : in O. moluccanum, also, the root 

 emerges early from the prothallus and projects downwards, but the 



