TRANSACTIONS OF SECTION K. 103D 



III. The fact tliat in cases of induced apogamy in Ferns arcbegonia are first 

 produced clearly shows that in these cases the first intention of the plant is 

 towards a normal production of embryos, while apogamy takes its place as a sub- 

 stitutionary growth. It may remain an open question how far direct apogamy 

 will bear a similar interpretation. 



IV'. The character of the aposporous and apogamous growths is very anomalous ; 

 their position is not definite ; aposporous growths may arise from the sorus and 

 sporangia, or from the most varied points on the margin or surface of the leaf. 

 With regard to apogamy in Ferns, it appears, as the result of a lartfe number of 

 observations, that though there is an average normal of position, still any one part 

 of the sporophyte — stem, leaf, ramentum, root, sporangium, or even tracheid — may 

 arise, independently of others, from the prothallus. Single sporangia, or groups 

 of them, may appear without vegetative organs of the sporophyte ; leaves without 

 other parts ; in one case, I believe, as many as ten roots have been seen without 

 any other members of the sporophyte ! The close similarity of the parts thus 

 irregularly placed to those formed in regular sequence in the normal plant shoidd 

 be a warning of their abnormality. I cannot see in them any suggestion of a 

 primitive state. Dr. Lang tells me that these exceptional developments form only 

 a small proportion of the individuals in any one culture ; still they are there, and 

 those who hold that apogamous developments are a suitable basis for morphological 

 argument must not pick and choose those cases which suit their views, but must 

 take even the most extravagant into carefal estimation. My own view is that 

 these anomalous growths are not a safe guide to past history. But looked upon 

 as the result of a recently acquired transition from one generation already estab- 

 lished to the other, following nuclear changes, in the one case of reduction after 

 insufficient nutrition, in the other of doubling of the chromosomes following on 

 plethora, apospory and apogamy are at least intelligible. We shall understand 

 how the transition may take place at one point or at many, while the irregularity 

 of the parts produced offers no morphological difficulty ; it is rather what might 

 have been anticipated if the transition were a ready consequence of the conditions 

 we have noted. 



Lastly, a word on Dr. Scott's utilitarian argument. He remarks : ' A mode of 

 growth whicli affords a perfectly efficient means of abundant propagation cannot, 

 I think, be dismissed as merely teratological.' We must be clear that utility is no 

 certain evidence of antiquity. As refuges for the physiologically destitute, 

 apogamy and apospory may play an important part noiu, and in so far are not to 

 be dismissed as mere freaks of Nature. But in my view they would rank, as 

 regards utility pure and simple, with the formation of adventitious buds on the 

 root-system of a Poplar that has been felled ; or with the bulbils which replace 

 the flowers in so many mountain species : neither these, nor, I think, aposporous 

 or apogamous growths, throw any direct light upon the story of descent. 



To sum up, then, not only do I find that the facts in our possession, including 

 the wildest anomalies, are consistent with an antithetic theory, but a comparison 

 of normal forms seems to me to support the opinion that the sporophyte has 

 appeared as the result of gradual elaboration from the zygote, a fresh phase having 

 been thus gradually intercalated in the course of evolution. This idea, first clearly 

 stated by Celakovsky in 1868, was developed by him in subsequent writings. I 

 endeavoured to place it on a footing of adaptation to external conditions in 1890 ; 

 and in 1897 we find Strasburger restating the position in terms almost identical with 

 my own, but upon a basis of nuclear detail which had not been dreamed of when the 

 view was first propounded. Dr. Scott has enthusiastically appreciated the double 

 verification of the forecasts of Professor Pringsheim ; I think that the way in which 

 the antithetic theory is found to work in with the nuclear details recently discovered 

 appeals quite as strongly to my mind. 



In the course of this discussion I have not been anxious to point out such 

 difficulties as beset the homologous view ; all I have attempted here has been 

 to set aside some of the difficulties which have been suggested in opposition to 

 an antithetic view, and to show that the latter theory will adequately cover the 

 facts. 



Returning now to our general inquiry on homology, we see that on' the 



