912 TRANSACTIONS OF SECTION K. 



Embrydoyy and Seedling'striicture. 



The view developed here is founded on the doctrine of anaphytosis aa opposed 

 to the monaxial theory of most observers. The typical plant represents a colony 

 of distinct inrfmc^wa/s or 'pliytons,' budding one out of the other as the 'stem' 

 grows in length {cf. formation of stationary colony of aphides). The possibility 

 of propagation by cuttings shows this to be the true interpretation. In the history 

 of such a colony the first individual Is the embryo. 



The main question is, does the embryo, or does it not, repeat in its structure 

 that of the group or race to which the ' plant ' belongs ? Every analogy from 

 the animal kingdom supports the view that it does. Nor is it likely that any 

 adaptive function acquired comparatively recently, however important, can have 

 obscured this primitive structure. If the stem had, in the whole ancestry of the 

 plant, always been the dominant organ and the leaf a subsidiary lateral one, it 

 would be expected that the plumular axis, and not the cotyledon, would have 

 assumed the role of an absorptive organ within the embryo-sac or of an assimilating 

 organ on germination. 



It is highly probable that the Angiosperm group, like every other group, 

 roughly recapitulates in its embryonic history the structure of the primeval 

 ancestor from which all groups have sprung. This latter is the primitive 

 Bryophyte. It is the archaic individual, showing, in its capsule, seta, and foot, 

 the fundaments and originals of the phyllome, caulome, and root respectively in 

 the vascular plants. The close correspondence in development of the three or 

 four main parts between the embryo of an Angiosperm and that of a Liverwort, 

 like Jungermannia biscuspidata, proves that the two are precisely homologous 

 structures. 



The facts of embryogeny in vascular plants are entirely opposed to, and 

 inconsistent with, the ordinary teaching that a plant consists of a single shoot on 

 which the leaves are borne as lateral appendages. This teaching is due to the 

 misleading ideas which arise as a result of the study of the later phases in the 

 ontogenetic development of the ' plant,' the importance of which has always been 

 too greatly insisted on. On the other hand, these embryological data are in 

 harmony with the sporogonial theory and the doctrine of anaphytosis. The first 

 one or two foliar organs begin to appear long before the axis : and the subsequent 

 development clearly shows how the leaves are the dominant organs and the axis 

 entirely subsidiary. The primary division of the embryo into an upper and a lower 

 set of quadrants shows that the former represents an organ of closed and limited 

 growth, viz., a foliar oigaii, and not a leaf-bearing axis of unlimited and indefinite 

 growth. This is due to the fact that each successive leaf is primitively terminal 

 to a segment of the axis, which would result in the leaf being large as compared 

 with the axis on which it is borne. 



Eventually the axis asserted itself precociously, and the leaves became pushed 

 over into a lateral position. Both conditions, the primary and the inauguration 

 of the secondary, occur in the embryonic history of Bryophytes {Jungefmannia 

 and Moss),Fern9 ( Ceratopteris and Polypodium), and Angio.'perms (Monocotyledons 

 and Dicotyledons). 



Inasmuch as in all these groups the first one or two leaves precede the stem 

 during the course of development of the various organs out of the homogeneous 

 thallus structure, it follows that in the primitive vascular plant, including the 

 primitive Angiosperm, there was in the first place a single leaf, terminal to the 

 stem, which by dichotomy gave rise to two leaves. 



Hence Monocotyledons must have preceded Dicotyledons ; for if the embryo of 

 the latter group does not represent in its history a repetition of the phases of 

 development of the ancestor, it must represent a case of extreme reduction, which 

 is an absurd supposition for such a highly advanced group as Dicotyledons. The 

 mouocotyledonous embryo is therefore the primitive sporogonium-like type, and 

 the dicotyledonous type has been derived from it, just as the dicotyledonous 

 embryo of Selaginella must have been derived by dichotomy of the single coty- 

 ledon of Lycopodium, 



