138 Professor Alexander Dickson on the 



represented an open carpel. He pointed out its position 

 in the axil of a bract, and argued that it must therefore 

 be axial in its nature. At the same time, however, be 

 adopted Brown's hypothesis of the ovular nature of the 

 female reproductive structure ; and accordingly looked upon 

 it as a placenta, — a view that, curiously enough, has in 

 recent years been revived, though in somewhat modified 

 form, by Professors Sachs and Eichler. 



In 1853, Alexander Braun,* on teratological evidence 

 afforded by Larch cones, in which the axis was prolonged 

 through the cone as a leafy branch (durchwachsene Zap- 

 fen), asserted that the squama was formed by the growing 

 together of two leaves. His view, as afterwards more 

 clearly explained by Caspary, who adopted it,t being that 

 the cone-scale consists of two carpels which are connate 

 and are the first leaves of a scarcely developed shoot spring- 

 ing from the axil of the bract. 



In 1860, Baillon| showed that the squama originates 

 as a mammilla in the axil of the bract, after the manner of 

 an axillary shoot ; and it may, I think, be looked on as 

 almost certain that a secondary axis does enter into its 

 constitution, if, indeed, it does not form the whole of it. 

 Baillon viewed the squama as representing an expanded 

 shoot or cladode ; and in this opinion I am strongly dis- 

 posed to concur. 



In 1869, Van Tieghem§ made a most important histo- 

 logical contribution to the subject, by showing that the 

 fibro-vascular bundles of the squama are so arranged that 

 their phloem elements are directed towards the upper, and 

 their xylem towards the lower surface. He suggested 

 that here we had an arrested axis giving origin to one 

 carpel or possibly two carpels (the number he left an open 

 question). If there was only one carpel, then it was 

 supposed to spring from the posterior aspect of the 

 secondary shoot; and if there were two, then these were 



* " Das Individuum der Pflanze, &c.," Ahkandl. dcr k. Akad. d. Wisseiisch. 

 zu Berlin, 1853, p. 81, note. 



+ Caspary, De Ahietincarum Carr. floris feminei structura morphoJogica, 

 Konigsberg, 1861, p. 4. 



+ Baillon, Becherches organog6niques sur la fleur femelle des Coni/eres, Paris, 

 1860, p. 6. 



§ Van Tieghem, "Anatomie de la fleur des Gymnospermes," ^?m. des Sc. 

 Nat., 5« Ser., Botanique, x. (18C9) p. 274, note. 



