Mr. J. Miers on Ephedra, 135 



now be necessaiy to pass in review the points of analogy that 

 exist between it and other exogenous orders, in order to judge 

 of its true affinities. 



Blume, when he founded the order, as before stated, suggested 

 the relationship of the Gnetacea with' Casuarina, to which genus 

 it certainly offers many points of approximation. Casuarina 

 resembles Ephedra in the following particulars : — in the vaginant 

 sheaths that encircle the nodes of its branchlets, where they 

 occupy the place of leaves ; in its spicated inflorescence, with 

 diclinous flowers ; in the persistence of the involucral leaflets, 

 which afterwards enclose the fruits ; in its bifid perigonium, even 

 more deciduous than that of Ephedra^ for it is carried away by 

 the stamen as it grows upward in the act of aestivation ; in its soli- 

 tary stamen, very analogous to that of Gnetum ; in its one-celled 

 ovary, with an ascending ovule ; and in its indehiscent one-celled 

 fruit, with a single erect seed, containing an embryo imbedded 

 in albumen, with a superior radicle. Casuarina, however, differs 

 from both Gnetum and Ephedra in its straight, lofty, solid, woody 

 trunk ; in its ovary with two lengthened styles (being probably 

 formed normally of two combined carpels, one of v/hich is always 

 abortive, and which contains two ovules) ; in its fruit, with a 

 samariform epicarp, a mesocarp replete with very numerous deli- 

 cate spiral vessels, and a solid testaceous endocarp ; and, finally, 

 in the development of its seed, the anomalous circumstances 

 attendant on which have been only imperfectly understood*. 



* I have examined the seeds of Casuarina equisetifoUa many times, 

 always with the same result ; and as my analysis shows a structure tery 

 different from what is recorded of it, I will state the details. The descrip- 

 tion given by Endlicher of this structure (Gen. Plant, p. 271) is altogether 

 incorrect. It is well known that the fruits are contained in globular or 

 oblong strobiliform heads, each separate fruit being enclosed in a cell 

 formed of two coriaceous valves, which are the persistent involucels of the 

 spicated flowers, which valves stand right and left in regard to the axis. 

 Each fruit is fixed to the bottom of its enclosure by a small basal hilum : 

 it is somewhat samariform, oblong and compressed ; the upper moiety 

 (being a portion of the extended epicarp) forms a thin membranaceous 

 wing ; the lower moiety is thickened and smooth, consisting of an inter- 

 mediate mesocarp filled with copious, white, spiral threads, and a testa- 

 ceous, brittle, obpyriform endocarp, completely 1 -celled and indehiscent, 

 and containing a single erect seed, which tapers to the apex. This seed 

 consists of two very delicate translucent membranaceous tunics : upon the 

 outer one (testa) is seen, imbedded in it, a thickened simple cord (raphe), 

 by one extremity of which the seed is attached to the bottom of the cell ; 

 this cord rises to near the middle of the integument, when it becomes 

 suddenly recurved downward for a short distance, where it terminates in a 

 darkish areole (chalaza) ; before its recurvature it throws out a short lateral 

 bratfch or free thread, which serves as the medium of attachment of an 

 abortive ovule at a point a little above its base, where this also is recurved 

 upon its basal chalaza. The abortive ovule, tapering upwards, is nearly 

 half the length of the fertile seed to which it is thus attached ; it is deli- 



