518 Royal Society. 



The nut also does not adhere to the fleshy cup except below its 

 middle. The internal structure is the same in all three. 



Such are the main facts which I have been able satisfactorily to 

 establish. There are many others yet to be worked out, especially 

 those connected with the individual tissues of which those bodies are 

 composed ; and it is particularly to be borne in mind that the disco- 

 very of some structure indicative of albumen or embryo, is abso- 

 lutely essential to the complete establishment of the affinity I have 

 suggested. 



It must not be overlooked, that the characters through which I have 

 attempted to establish an affinity between Trigoiwcarpon and Coniferse 

 are equally common to the fruits of Cycadese; and in connexion with 

 this subject I may remark, that M. Brongniart* has referred the 

 genus Noggerathiu, which is also found in the coal-measures, to 

 that natural order, together with some associated organs which are 

 probably Trigonocarpons in a mutilated state. The leaves of Nog- 

 gerathia are, however, alone known, and Dr. Lindley, when figuring 

 those of one species (Lindley and Hutton, Fossil Flora, 28, 29), 

 pointed out their great resemblance to those of Salisburia, thus 

 affording collateral evidence of the view I have been led to adopt 

 from an examination of the fruit alone. 



April 6. — Thomas Graham, Esq., V.P., in the Chair. 



The following communication was read : — " On a new Series of 

 Sulphuretted Acids." By Dr. August Kekule. 



Adopting the idea that the series of organic compounds of which 

 sulphuretted hydrogen is the type, corresponds in every respect with 

 the series of which water is the type, I concluded that not only 

 mercaptans and neutral sulphides which correspond to the alcohols 

 and aethers, but also compounds corresponding to the acids, anhy- 

 drous acids and sethers of acids might be produced ; I therefore 

 endeavoured to obtain reactions which would enable me to replace 

 oxygen in the compounds of the latter series by sulphur. 



Such reactions are produced by the compounds of sulphur with 

 phosphorus — the tersulphide (F- S') and the pentasulphide (P^ S*) — 

 which are easily obtained by fusing together amorphous phosphorus 

 and sulphur in an atmosphere of carbonic acid ; no explosion takes 

 place, although the combination is attended with a very violent 

 action. 



Experiment has proved that these combinations of sulphur and 

 phosphorus act on the members of the series of water in the same 

 manner (although less violently) as the corresponding compounds 

 of chlorine and phosphorus ; — however, with this diflference, that by 

 using the chlorine compounds the product is resolved into tioo groups 

 of atoms, while by using the sulphur compounds there is obtained 

 only one group ; a peculiarity, which, according to the bibasic nature 

 of sulphur, must have been expected. By acting on these com- 

 pounds of sulphur and phosphorus with water one atom of sulphu- 



* Amiales des Sciences Nalurelles, 2"'' Series, vol. v. p. 52. 



