GNETALBS 



119 



Gymnosperms. The root cap is derived in the same way from 

 the outer exfoliating layers of the periblem, and the primary 

 vascular cylinder is diarch. 



II. THE SPORE-PRODUCING MEMBERS 



THE MICEOSPOEANGIUM 



So far as vi^e can discover, there is no recorded information 

 as to the development of the microsporangium in Gnetales, but 

 presumably it foUoves the general sequence common to Gymno- 

 sperms and Angiosperms. The foUov^ing account, therefore, 

 can deal only veith the gross structure of the so-called staminate 

 flovcers. 



Ephedra. — The flowers are monosporangiate, and are borne 

 in the axils of bracts in a spicate inflorescence. The staminate 



Fig. S^.— Tumhoa : A, young staminate flower; £, older staminate flower, with the 

 sterile ovule in the center : C, two stamens ; D, the sterile ovule ; H, the ovulate 

 flower, showing tubular mioropyle (») and winglike expansions of the " perianth " ; 

 F, the same after fertilization ; ff, longitudinal section of a ripe seed, showing con- 

 spicuous suspeusor (s).— After Stbasedkgee, the figure being -taken from Enqleb 

 and Pbantl's Nat. Pflanzenfam. 



flower consists of two more or less connate scales (" perianth ") 

 investing a projecting axis, which bears two or more sporangia. 

 The sporangia appear to be cauline, the sporangiferous axis re- 

 maining simple and bearing two sporangia, or branching some- 

 what above and bearing several sporangia (Fig. 83). 

 9 



