292 RETIREMENT, TO 1897 : BOTANICAL WORK 



be made justified Hooker in considering it to be a sporangium 

 of a Lycopodium or allied plant. 



In 1875 more specimens were discovered in the West 

 Malvern limestones, and sent to Hooker through Mr. Symonds 

 of Pendock. Sections made convinced Hooker (as also various 

 cryptogamists) of its structural connexion with the Algae, 

 though there was much difference as to its existing affinities. 

 A stumbling-block was the apparent discontinuity between 

 the filaments of its inner cavity and the tissues of the sur- 

 rounding walls, which even suggested the possibility that 

 the former belonged to an intruded parasitic alga, or the 

 mycelium of a parasite. 



Similar bodies were constantly found in Great Britain 

 and in America, and in 1882 Principal (Sir J. W.) Dawson 

 of Toronto communicated a paper on the subject to the Geo- 

 logical Society. In his view Pachytheca was a seed, rather 

 than a spore case, belonging to a primitive form of Gymno- 

 sperm (Prototaxites). But his arguments did not find much 

 support ; others variously suggested that it was the float 

 of a seaweed, or even of animal origin ; Professor Thiselton- 

 Dyer, who believed he had detected the missing connexion 

 between the contents of the cavity and the wall, traced a 

 morphological affinity to Codium in both Pachytheca and 

 Prototaxites, but saw no evidence of the former being a 

 sporangium of the latter. 



All through the eighties Hooker sought more light, and 

 corresponded with various investigators. Professor (Sir E.) 

 Bay Lankester confirmed his general views ; the specimens 

 were examined by the Rev. J. D. La Touche, himself a 

 keen r geolo gist, who was publishing the local geology for the 

 Shropshire Natural History Society ; Mr. W. Phillips, the 

 algologist of Shrewsbury, propounded a definite form of the 

 parasitic view which on many grounds Hooker considered 

 untenable. 



Robert Etheridge, 1 President of the Geological Society in 

 1880-81, who had ' again and again examined these bodies/ 



1 Robert Etheridge contributed various papers to the Memoirs of the Geo- 

 logical Survey of New South Wales, 1888-94. 



