68 MORPHOLOGICAL DEVELOPMENT. 



sive fronds to each other. The modified relations that would 

 result, if the nutrition of the embryo admitted of anticipatory 

 development of the successive fronds, is shown in Fig. 117. 

 And how readily the structure may pass into that of the 

 monocotyledonous germ, will be seen on inspecting Fig. 118 ; 

 which is a vertical section of an actual monocotyledon at an 

 early stage — the incomplete lines at the left of its root, indi- 

 cating its connexion with the seed* Contrariwise, 

 where the strength required for maintaining an upright atti- 

 tude is not obtained by the rolling up of the fronds, but by 

 the strengthening of the continuous mid- rib, the second 

 frond, so far from being less favourably circumstanced than 

 the first, becomes in some respects even more favourably 

 circumstanced : being above the other, it gets a greater share 

 of light, and it is less restricted by surrounding obstacles. 

 There is nothing, therefore, to prevent it from rapidly gaining 

 an equality with the first. And if we assume, as the truths of 

 embryology entitle us to do, an increasing tendency towards 

 anticijDation in the development of subsequent fronds — if 

 we assume that here, as in other cases, structures which 

 were originally produced in succession, will, if the nutrition 

 allows and no mechanical dependence hinders, come to be pro 

 duced simultaneously ; there is nothing to prevent the pas- 

 sage of the type represented in Fig. Ill, into that represented 



* Since these figures were put on the block, it has occurred to me that the 

 relations would be still clearer, were the primary frond represented as not taking 

 part in these processes of modification, which have been described as giving rise 

 to the erect form ; as, indeed, the rooting of its under surface will prevent it from 

 doing in any considerable degree. In such case, each of the Figs. Ill to 117, 

 should have a horizontal rooted frond at its base, homologous with the pro-em- 

 bryo among Acrogens. This primary frond would then more manifestly stand in 

 the same relation to the rest, as the cotyledon does to the plumule— both by 

 position, and as a supplier of nutriment. Fig. 117 a, which I am enabled to 

 add, shows that this would complete the interpretation. Of the dicotyledonous 

 series, it is needful to add no further explanation than that the difference in habit 

 of growth, will permit the second frond to root itself as well as the first ; and so 

 to become an additional source of nutrition, similarly circumstanced to the first 

 and equal with it. 



