OLIVE-BROWN SEAWEEDS. 245 



The discovery of cryptostomata in the sori of Ade?wcystis 

 and Hydroclathrus seemed to point to rudimentary con- 

 ceptacles, or, if it be preferred, ancestral ones. This 

 evidence might be made to fit without violence into the 

 general scheme of seeking shelter of the kind for reproduc- 

 tive bodies. We have, however, to reckon with the fact 

 that in other forms the cryptostomata occur apart from the 

 sori, and it is precisely this kind of obstinate fact that shows 

 us the futility in the present state of evidence of guessing 

 at the relative antiquity of conceptacles and cryptostomata. 

 If anything" it favours Miss Barton's view that they are "of 

 equal antiquity, and that neither is an outcome of the 

 other ". 



The search, however, among the Laminarian sori for 

 evidence of curling up, of seeking the shelter so provided, 

 has been rewarded in the cases described by Miss A. L. 

 Smith and Miss Frances Whitting (8). The sporophyllous 

 leaves of Postehia and the gigantic Macrocystis are fur- 

 rowed longitudinally with parallel trenches, and it is within 

 the shelter of these trenches that the sori of sporangia are 

 placed. So perfect is this adaptation that a transverse sec- 

 tion of the leaf (see plate xx., figs. 2 and 5 of their memoir) 

 would appear to show the effect of a series of conceptacles like 

 those of Splacknidium. Of course this appearance is shown 

 only in transverse section, and proves nothing more than 

 that it is an adaptation to the same end as a conceptacle, of 

 a less perfect kind probably, at all events of a simpler kind. 



I have cited these instances and considerations with no 

 pretence of offering an adequate explanation of the puzzles 

 to be found in this subject, but rather with the hope of 

 showing that the conceptacles and cryptostomata of the 

 FucacecB are not isolated phenomena, but part merely of a 

 series showing the same character and tendency, and called 

 forth to meet like requirements. 



Recent attempts to classify the orders of olive-brown 

 algae have been characterised for the most part by too 

 much being made of the differences between them. This is 

 a very natural thing under the circumstances, but it is 

 occasionally well for us to dwell rather on the resemblances, 



