GXETALES 



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 SPOKE-PRODUCING MEMBERS 



THE MICEOSPOEANGIUM 



So far as we can discover, there is no recorded information 

 as to the development of the microsporangium in Gnetales, but 

 presumably it follows the general sequence common to Gymno- 

 sperms and Angiosperms. The following account, therefore, 

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

 flowers. 



Ephedra. The flowers are monosporangiate, and are borne 

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



FIG. 86. Tumboa', A, young staminate flower; .Z?, older staminate flower, with the 

 .sterile ovule in the center : f, two stamens ; Z>, the sterile ovule ; E, the ovulate 

 flower, showing tubular micropyle (i) and winglike expansions of the " perianth " ; 

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

 spicuous suspensor (s). After STRASBURGER, the figure being taken from ENGLER 

 and PRANTL'S Xat. 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 



