390 BOTANICAL GAZETTE [November 



authors give the name "Hemiangiospermeae." To this hypothetical group the 

 Bennettitales are related, but are specialized in their own way. 



The living angiosperms most nearly related to the "Hemiangiospermeae" 

 are the Ranales, especially the Magnoliaceae, whose probable primitive position 

 has begun to force itself upon the attention of morphologists ever since Wieland's 

 studies of Bennettitales; and from this same Ranales plexus the monocotyledons 

 probably diverged. The monophyletic origin of angiosperms is maintained, but 

 to the reviewer it seems altogether probable that while a simple strobilus, like 

 that of Bennettitales, resulted in such a flower as that of the Ranales, a compound 

 strobilus, like that of the Gnetales, may have resulted in such an inflorescence as 

 an ament. 



4 



An inevitable suggestion is that the pteridosperms developed in the Mesozoic 

 by two distinct methods: (i) by sporophylls aggregated into monosporangiate 

 strobili leading to the modern cycads; (2) by both kinds of sporophylls massed 

 into one amphisporangiate strobilus, as in Bennettitales, 



The paper contains many interesting and suggestive details which cannot 

 be mentioned here, and it brings together in every useful form views which have 

 been working like leaven, but which had not been expressed. 



Another paper dealing with the method of origin of angiosperms, rather 

 than with their phylogeny, is that by Cook.^<* It is a theoretical discussion of 

 the possibility of angiosperms arising directly from liverworts, such as Anthoceros, 

 through the persistent aposporous development of the prothallia, which serve 

 "as means of attachment for the young plant during its embryonic stages. 

 *' Apospor)' need not interfere with the formation of sex cells, nor with the continu- 

 ation of truly sexual methods of reproduction." It seems that in this elimination 

 of spores "mitapsis*' is simply deferred to later generations of cells, in angio- 



■ ■ 



sperms being carried over into the aposporous female prothallium. From an 

 Anthoceros capsule an angiosperm with two cotyledons could be derived; and 

 then a many-leaved stem could be built up by the successive addition of "meta- 

 mers." The elimination of megaspores in the life-history of angiosperms results 

 in such new interpretations of structure that the reviewer must confess he is unable 

 to follow the discussion. For example, "the part of the angiosperm which, in 

 the present view, might correspond to the prothallus itself, is the nucellus. And 

 even this relation would not be direct, for the nucellus of the angiosperms might 

 not be homologous with the nucellus of the conifers and cycads, which, if current 

 interpretations are correct, is more analogous to the placenta of the mammal than 

 to an aposporous prothallus." Also, "the g5minosperms may be supposed to 

 have the ovules and seeds naked because they are still borne in an endosperm 

 which corresponds to the primitive, vegetatively functional prothallus, though it 

 now remains attached to the much more highly developed double-celled structure 

 which corresponds, in turn, to the capsule of the liverwort and the moss, the 



37 



10 Cook, O. F., Origin and evolution of angiosperms through apospory. iFroc 

 Wash. Acad. Sci. 9:159-178. 1907. 



