310 RevieiD of the J^atural Order Cycadacece. 



lution of which has not taken place, and the seeds are conse- 

 quently left naked upon its face or margin,) but from their simi- 

 larity to other plants, in the structure of the seeds themselves, 

 having the same integuments, the same foramina in the ovula and 

 mycropyle in the mature seed, with only such "slight deviations 

 in structure as might be expected, from the peculiar economy of 

 their orders." 



" A resemblance in inflorescence, fructification, and need, are not the 

 only points of agreement between Cycadacea; and Coniferai. The sim- 

 ple cyliudrical stem of the former, which resembles outwardly the trunk 

 of the palms, (a Monocotyledonous order,) has been shown, by M. 

 Brongniart, to be decidedly exogenous in structure — probably only grow- 

 ing in the form of a simple trunk, iu consequence of the non-develop- 

 ment of the axillary buds. The leaves of both the Cycas and the fir 

 tribes, as Prof. Lindley remarks, have the same parallel arrangement of 

 veins, and both tribes exhibit a marked similarity in the fewness of their 

 spirai vessels. Cycadacea? and Coniferte still farther agree in a char- 

 acter lately discovered, as unique as it is important, and which alone 

 would establish the fact of a strong affinity existing between the two 

 orders; namely, the singular perforations in, or rather globules adherent 

 to, the fibres of their wood, to which there exists nothing analogous in 

 the structure of any other tribe of plants.* 



" Placed thus, as it were, at the lowest step, in the gradation of plants 

 which have a vascular system and an exogenous structure, Gymnosper- 

 nnce approach closely in their affinities to flowerless plants, through the 

 Cycadacea3, which have mostly the same gyrate vernation as the ferns, a 

 manner of producing their seeds upon the margins of the leaves, anala- 

 gous to the production of the thecfe in Osmundaceae, and the same pin- 

 nated foliage and simple columnar trunks as some of the arborescent 

 ferns. They are also related to Equisetacese by a similar simplicity of 

 structure in the female organs, if the sporules of that singular order 

 are really naked ovula, as is very jdausibly suggested by M. Ad. Brong- 

 niart. At least the resemblance of those organs to the female flower 

 of Zamia is in the highest degree obvious and striking. 



" But the relation between the ferns and other flowerless plants, and 

 CycadacccB and Coniferfe, as well as the importance of these orders in 

 former times, can only be properly appreciated by those who have paid 

 attention to fossil botanj^, and are acquainted, by means of that inter- 

 esting science, with the primitive flora of the globe. In those remote 

 ages, when ferns and marine Algse, Equisetacea;, and Lj'copodiacese, 

 with Cycadacete, Coniferfe, and a few palms, constituted the whole of 

 the vegetable kingdom, these orders occupied a much more conspicuous 

 station than at the present day. At that |)eriod, when, as geology has 

 now iucontestibly j)roved, the globe was tenanted by a 'race of reptiles^ 

 — (those strangely formed animals, the aquatic and amphibious Sauri- 

 ans, which existed before the formation of the secondarj' strata,) — the 

 vegetation of the earth was also in a corres])onding primitive state of 

 organization. Cellulares or flowerless jdants covered the greater por- 

 tion of the globe; among which were Equisctacea3 of enormous size, 



* " So permanent is this characteristic, that geologists have recently through it identi- 

 fied Coniferous wood, which lias been imbedded in the coal siiuta lor thousands of years! 

 Messrs. Nicol and Wilham, hy grinding down to very thin jilatcs srclions of fossil woods, 

 have been able to call in the microscope to their aid, and liave ascertained their structure 

 in tiic most satisfactory manner. Their examinations liave led tiiein to the conclusion, 

 that all known exogenous fossil woods belong either to Coniferie or Cycadacea;." 



