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1914. The spur shoot of the pines. Bot. Gaz., 17:362-385. 



1927. Evolution of the seed habit in plants. Trans. Roy. Soc. Canada, ser. 3, 21: 



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1925. Resin canals in the Canadian Spruce [Picea canadensis (Mill.) B.S.P.]. An 

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TiEGHEM, P. VAN 



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1886. Sur la polystelie. Ann. Sci. Nat. Bot, ser. 7, 3:275-322. 



1888. Recherches comparatives sur I'origine des membres endogenes dans les plantes 

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Unger, F. 



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Walton, J. 



1928. On the structure of a Palaeozoic cone-scale and the evidence it furnishes of the 

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