APPLICABLE WITHIN LIMITS 185 



cotyledons or protophylls raise any insuperable obstacle in the way of a 

 theory of the strobilus as stated in a previous chapter, so long as they 

 are held to be anticipatory growths in the sense above explained. 



From the above pages it will be seen that the foundations of recent or 

 current embryology of the sporophyte are open to criticism. The analogies 

 with animal embryology are misleading : strict recapitulation is not to be 

 assumed where, as in plants, continued embryology holds sway : segmenta- 

 tion appears to be a phenomenon connected in no obligatory sense with the 

 origin of organs : the relative position of the parts of the embryo, though 

 it may be fairly uniform in circles of near affinity, is variable according 

 to biological requirements which are readily intelligible in the establish- 

 ment of the germ : the relative time of origin of the parts may also be 

 variable, even within circles of near affinity. The question will therefore 

 be what weight in our comparisons is to be accorded to these somewhat 

 fluctuating facts of the primary embryogeny of the sporophyte? They 

 have been very highly estimated in the past: while not denying their 

 value, I think that they have been given altogether undue precedence over 

 the characters of the sporophyte which appear later, and this opinion is 

 based both on general considerations and on detailed comparison. Accord- 

 ing to the view of alternation advanced above, there does not appear to 

 be any sufficient reason for attaching special comparative importance to 

 the initial steps of the primary embryology. If it had not been for the 

 recapitulation theory of the zoologists, it is improbable that this position 

 would ever have been adopted in the case of plants. The more natural 

 inference from the facts would probably have been the converse, that is, to 

 attach greater weight to the characters of the mature shoot : in fact, the 

 position now is that the embryogeny must be interpreted in terms of the 

 mature plant rather than the converse which a recapitulation theory would 

 demand. For the reasons thus stated the initial embryogeny of the sporo- 

 phyte will be accorded only a minor place in our comparisons : when 

 once the earlier, and in considerable degree adaptive embryonic phase 

 is past, and the form characteristic of the mature plant is by way of 

 being established, this would seem to be a more reliable basis for com- 

 parison than any minute details of the initial embryogeny. 1 Probably the 

 strobilus itself will give the y most trustworthy basis of all. 



hut it is not to be concluded that recapitulation plays no part whatever 

 in the development of the sporophyte. Seedlings of many plants with 

 highly specialised shoots, such as the phyllodineous Acacias, and spinous 

 plants such as Ulex, start with a postcotyledonary shoot of simple and 

 not specialised form, characteristic of the group to which they belong: 

 they only assume their peculiarly adaptive character later. They thus 

 reflect in some degree in their ontogeny the history of their specialisation. 

 Such facts are familiar, and the interpretation generally accepted. But 



Thomas (New Phytologist, 1907, p. 77, etc.) has expressed a similar view as 

 applied to the embryogeny of Angiosperms. 



