May 30, 1907 J 



NATURE 



115 



a gymnosperin. This plant, and a few of its immediate 

 allies, afford the only instances, so far I<nown, of the 

 preservation of the embryo in a fossil seed.' 



In the whole arrangement of the floral organs, the 

 presence of a pericarp, and the character of the seed, the 

 fructification differs entirely from anything known in 

 gymnosperms, and the inclusion of Bennettites in Saporta's 

 class " pro-angiosperms " appeared justified on grounds 

 of analogy if not of affinity. 



So far, however, nothing whatever was known of the 

 staminate organs of these plants, and no one suspected 

 that the fructifications already known were other than 

 unisexual. The complete elucidation of the subject was re- 

 served for the American palaeontologists, who possess a 

 wealth of material for the investigation of Mesozoic 

 Cytadophyta far exceeding anything that Europe can show. 

 No less than sixty species of silicified cycadean trunks 

 have now been described from the Mesozoic of America, 

 ranging from the Upper Triassic to the Lower Cretaceous. 



The specimens are often extremely numerous ; thus the 

 twenty-nine species from the Black Hills of South Dakota 

 are represented by nearly 1000 more or less complete trunks. 

 In fact, the Cycadophyta of the American Mesozoic are as 



Fig. 2. — Cycad<:oidt-a iitgcns. 

 section, showing the centi 

 synangia, and the surroun 

 Wieland's "American Fo 



»I ovuliferous cent 

 ling bracts, hairy v 

 sil Cycads." 



important to the botanist as the gigantic saurians (with 

 which they are often associated) are to the zoologist. 



Fig. I represents the first American fossil cycad ever 

 discovered ; it was found about i860 in Maryland, between 

 Baltimore and Washington, by the geologist, Philip Tyson, 

 and well illustrates the external features of the group. 

 K third of a century elapsed before any further discoveries 

 were made, so the present magnificent material has been 

 accumulated within quite a short period. The systematic 

 arrangement of the specimens has been principally the 

 work of Prof. Lester Ward, while the morphological in- 

 vestigation has fallen to the share of Dr. Wieland, of 

 Yale University, to whom the discoveries we have now to 

 consider are due. In referring to Dr. Wieland's work, T 

 shall follow him in using the name Cycadeoidea, but it 

 must be understood that this is synonymous, so far as we 

 can tell, with Bennettites. 



In external features, as well as in anatomical structure, 

 the .American species so far investigated agree wonderfully 

 closely with the European species of Bennettites, but it 

 must be remembered that the vast extent of the inaterial 

 will necessitate many years of arduous research before its 



1 Solms-Laubach, "On the Fructification of Bcmuttlics Gibso 

 English translation in .Ann. of Eot., v. iBgi. 



investigation can be completed. During the eight years 

 or so that Dr. Wieland has been at work, a marvellous 

 amount has been accomplished. His results are embodied 

 in a magnificent volutne issued last August by the Carnegie 

 Institution of Washington.' 



The male organs of the BennettitejE were first found in 

 1899, in the species Cycadeoidea ingens.- Two years later 

 the important fact was established that the organs of both 

 sexes occurred in the same fructification, the whole thus 

 constituting a " hermaphrodite," or bisexual flower.' 

 Twenty-five trunks bearing bisexual flowers have now been 

 investigated, belonging to seven American species. The 

 conditions in Cycadeoidea dacotensis, one of the cases 

 most fully investigated, are as follows. The whole fructifi- 

 cation has a length of about 12 cm., and protrudes beyond 

 the leaf-bases of the trunk. .About half the length is 

 occupied by the peduncle, the upper part of which bears 

 100 or more spirally arranged bracts, enclosing the essential 

 organs. The centre is occupied by the ovuliferous cone, 

 about 4 cm. in height, corresponding to the receptacle, with 

 its seeds and other appendages, as found in Bennettites 

 Gibsonianus. In C. dacotensis, however, the stage of 

 development is far earlier, immature ovules taking the 

 place of the ripe seeds of the more 

 advanced European specimens. We 

 have to do, then, in this case with an 

 organ in the stage of a flower, as dis- 

 tinguished from the fruit previously 

 described. The ovuliferous cone, or 

 gynfficium, is completely surrounded by 

 the hypogynous staminate disc, as Dr. 

 Wieland calls it, springing from the 

 riiTi of the receptacle at the base of the 

 cone (see diagram. Fig. 2). The 

 stamens are numerous (eighteen to 

 twenty in C. dacotensis), and arranged 

 in a whorl ; their stalks are united to 

 form a continuous sheath, which ex- 

 tends to about the level of the top of 

 the gyn^cium. Here they become free 

 from each other ; each stamen is a 

 compound, pinnate sporophyll, about 

 10 cm. long altogether, and is folded 

 inwards towards the gynaecium, the 

 deflexed tip reaching down nearly to 

 its base. The alternate pinnri, of 

 which there are about twenty pairs, 

 are likewise bent inwards. The pinnje, 

 with the exception of those at the apex 

 and base of the frond, which are 

 sterile, bear the pollen-sacs in two 

 rows, ten in each row on the longest 

 .\panded bisexual flower in longitudinal pinna;. Thus the Stamens are highly 



the compound stamens beating numerous complex organs, resembling the fertile 



hramenta. About half natural size. From fronds of a fern rather than the stamens 



to which we are accustomed in our 

 modern flowering plants. The com- 

 plexity, however, does not end here, for each pollen-sac 

 is itself a compound structure containing two rows of 

 loculi, ten or more in each row. It thus constitutes a 

 synangium, comparable to that of the marattiaceous ferns, 

 and especially the genus Marattia. The similarity to the 

 fructification of such a species as Marattia Kaulfussii is, 

 in fact, surprisingly close. 



It appears that all the specimens actually investigated 

 were in the bud condition, the stamens being still infolded, 

 as described above. Presumably the stamens eventually 

 opened out, and the diagrams introduced in Figs. 2 and 3 

 show them in the expanded condition. The ground-plan 

 of the open flower, shown in Fig. 3, is based on 

 Cycadeoidea ingens, a species in which the number of 

 stamens is smaller than in C. dacotensis. 



The leading features in the organisation of the 

 Bennettitean flower may be briefly recapitulated as 

 follows : — The centre is occupied by the gynsecium, seated 

 on the convex receptacle, and consisting of numerous long- 



F.y G. R. Wieland (19-6). 



Fossil Cycads." Part i. The Male 



Fossil Cycad 



2 "A Study of some / 

 Flower of Cycadeoidea. ; 



3 Op.cit., Part iv. On thi 

 .Amer. Journ. Science, xi.. 



isporangiate Fructification of O'^'dt/f't'/V/e'a, 



NO. 1 96 I, VOL. 76] 



