474 



NATURE 



[October 13, T910 



has, however, figured several impressions of herbaceous 

 Lycopods from the Palieozoic and Mesozoic rocks, some of 

 wliich appear to be similar in habit to the recent 

 Lycopodium, and others to Seloginella. The latter have 

 dimorphic leaves, and in some cases the sporangia are 

 aggregated into stroboli, while, in at least one species, they 

 are borne in the axils of foliage leaves, a very interesting 

 feature in comparison with the modern Selaginellas. 

 Zeiller, in his fine memoir, " Bassin houiller et permien 

 d3 Blanzy et du Creusot " (1906), has figured, among other 

 very interesting impressions, a Selaginellites, in which the 

 leaves are arranged in the same manner as in the recent 



tetrastichous Selog- 

 inellas. The hetero- 

 sporous cones con- 

 tain a large number 

 of megaspores in 

 the megasporangia, 

 another interesting 

 feature unknown in 

 the modern repre- 

 sentatives of the 

 group. 



These specimens, 

 however, are mere 

 impressions. F o r- 

 tunately, however. 

 Miss Benson ' has 

 recently extended 

 our knowledge of 

 these plants by 

 describing the 



anatomy and fruc- 

 tification of Miad- 

 esmia membranacea, 

 Bertr., the first 

 instance in which 

 we have any information as to the structure of a 

 herbaceous Pala;ozoic Lycopod. The fructification of 

 this plant proves to be a primitive seed-like organ, re- 

 calling Lepidocarpon among fossils, and Isoetes among 

 living plants. 



Numerous other memoirs on Palaeozoic Lycopods 

 have also appeared, which it is impossible to discuss 

 here, .'\mong these may be mentioned Prof. Weiss's = 

 description of a Stigmaria with centripetal wood, Mr. 

 Watson's^ discovery of the cone of Bothrodendron 

 munduni (Will.), and Mr. David White's* Archaeo- 

 sigillaria primaeva, an interesting impression from the 

 Devonian rocks of New York State. 



Although, as has been stated, no further attributions 

 cf seeds to the Palaeozoic fern-like plants or Pterido- 

 spermeae have been made during the last few years,' 

 our knowledge of this group has been extended in other 

 directions. Scott ' has described a new stem, Sutcliffia 

 insignis, Scott, a member of the Medullosea;, charac- 

 terised by concentric petiolar bundles, and a stem of 

 very simple structure with a single main stele ; a 

 unique case of dialystely without siphonostely. 



The structure of isolated seeds of pteridospermous 

 affinity has also received attention, Scott and Maslen's ' 

 studies of Trigonocarpus, of which the first part has 

 appeared, and Oliver's' memoir on Physosioma 

 elegans, Will., being notable contributions in this 

 direction. 



Turning next to the studies of Mesozoic plants, 

 Wieland's elucidation of the cone of Bennettites, to f 

 which we have already alluded, has been followed by 

 the very important discoveries by Nathorst ' of the 

 male organs of Williamsonia, Anomozamites (now called 

 Wielandiella), and several other genera of Triassic or 



Jurassic age, also belonging to the Bennettitales. 

 Nathorst's specimens were impressions and not petrifac- 

 tions, but by means of his new methods for studying 

 carbonised impressions ' he has been extremely successful 

 in obtaining, from mere impressions, information which, 

 until a few years ago, would have been regarded as quite 

 impossible. 



Nathorst finds that the flowers of Williamsonia, unlike 

 those of Bennettites, are unisexual, a very important point, 

 i'he male sporophylls (Fig. 3) were arranged in a whorl, 

 and were fourteen or fifteen in number. They were united 

 laterally for nearly half their length. The microsporangia 

 were borne on the inner side of the sporophyll on segments 

 which were somewhat divided. The male organs may be 

 of a similar nature to the extraordinary " male-fronds " of 

 Bennettites, but in Williamsonia they are very greatly 

 reduced. 



In Wielandiella, however, the cones are amphi- 

 sporangiate, and the male sporophylls are still more 

 reduced, and form a palisade-like ring near the base of the 

 cone. The cone was markedly protogynous (Fig. 4). 



The f.act that the male sporophylls of some members of 

 the Bennettitales have now been found, which are very 

 much reduced as compared w^ith those of Bennettites itself — 

 an event which was confidently expected to occur — has an 

 important bearing on the question of the origin of the 

 .-\ngiospcrmous stamen. - 



Wieland " has also recently described a male flower of a 

 Williamsonia, which does not, apparently, agree exactly 

 with that discovered by Nathorst in Yorkshire last summer. 

 On this specimen Wieland has founded a theory of the 

 phylogeny of the Gamopetala;, which, however, will prob- 

 ably not meet with general acceptance. 



Mesozoic plants are now attracting a more considerable 

 share of attention than they have in the past. The great 

 drawback to studies of this nature has always been the 

 absence of petrified material. ' Impressions alone are avail- 

 able, though there has been no lack of large, isolated stems 

 or trunks of Gymnospermous or .Angiospermous aHSnity in 

 certain deposits belonging to this period. Such petrifac- 

 tions, however, do not tell us very much, and we have 

 hitherto failed to find plant-bearing concretions, similar to 



, Phil. Trans. Roy. So 

 Ann. of Bol , vol. xxii 

 1, Mem. and Proc. Mar 



>I cxci.\., p. 409, 1908. 



■'Lit. and Phil. Soc, vol. Hi., No. 



i White, New York Stale Mus. HuP. cvii. 



^ Nathorst has shown that the fructificatii 



iiolMus Nalhorsti (Ann. of P. .t , vol. xxii., 



Linn. Soc. Lond., 

 "' Scott and Maslen, Ann. of Bot., 

 8 Oliver, Ann. of Bot., vol. xxiii., ] 

 '■> Nathorst, K. Svenska Velenskap. Akad.'Hi 



NO. 2137, VOL. 84] 



ns figured by Arber 

 p. 57, t9o8) are not « 

 ' ■ P- 45, 



p. S9, 1907. 

 ndl., vol. xlv., No. 4, 1909. 



3.— The Male Flower of Willi. 

 Lower Oolite of Whitby, Vorkjh 



the coal-ballsvof the English Carboniferous rocks, with their 

 wealth of fragments of leaves, cones, or other organs, from 

 which so much can be ascertained, both from an anatomical 

 and a phylogenetic standpoint. Stopes and Fujii ■* have 

 now, however, discovered such concretions in the Upper 



1 Nathorst, Arkiv. fiir Bolanik, vol. vii.. No. 4, 1907 ; K. Svenska Ve- 

 tenskap. Akad. Handl.. vol. xliii.. No. 6, 1908. 



See also Bather, Geol. Mag., Dec. v., vol. iv., p. 437, 1907 ; vol. v.. p. 454, 

 1908. 



2 See Arber and Parkin, ante. 



3 Wieland, Bot. Gaz., vol. xlviii., p. 427. 1909. 



■> Stopes and Fujii, Phil. Trans. Roy. Soc. B, vol. cci., p. i, 1910. 



