10 MORPHOLOGY OF SPERMATOPHYTES 



forms. That the form is Anabaena, and that there is but a sin- 

 gle species, are both doubtful statements. The cortical cells ad- 

 jacent to the chamber send out papillate prolongations into it, 

 giving in cross section the appearance of cells radially elongated. 



That the Algae are not the inciting cause of the excrescent 

 growth is apparent from the fact that it begins before the Algae 

 enter, and also from the fact that in some of the tuberclelike 

 rootlets Algae do not occur. The relations existing between the 

 fungous and algal elements without and within the plant, and the 

 root system, with its response in excrescent growth, lenticels, 

 cortical chamber, and internal cortical papillae, must be very 

 complex. 



The root cap is said by De Bary 13 to arise by the splitting 

 off of the outer layers of the periblem which covers the meri- 

 stematic region, there being no true calyptrogen or dermatogen. 

 This character is asserted by De Bary to be common to all Gym- 

 nosperms, in which they differ decidedly from Angiosperms. 



II. THE SPORE-PRODUCING MEMBERS 



THE MICKOSPORANGITJM 



Oycads are dioecious, and the staminate strobilus in Cycas, 

 at least, is terminal; but its true position in the other genera, 

 although apparently terminal, remains in doubt. Strobili may 

 occur singly or several together, and in the latter case some at 

 least are certainly lateral. The numerous sporophylls are 

 arranged in a close spiral (Figs. 8, 9). 



The sporophylls are persistent, often becoming very hard, 

 and compared with those of other groups are remarkably large. 

 In certain genera, as Cycas, Macrozamia, Ceratozamia, Stan- 

 geria, etc., they have the form of ordinary heavy scales. The 

 horizontal portion is narrowed at the insertion and broadens 

 outward, bearing beneath the very numerous sporangia, some- 

 times as many as one thousand ; while it is continued into a 

 more or less vertically expanded and sterile terminal region, 

 which is usually hairy without. In other genera, as Zamia, 

 the horizontal and vertical portions of the sporophylls become 

 more distinctly differentiated, the former becoming a slender 

 stalk, the latter a peltate expansion beneath which the sporangia 

 are clustered, as in Equisetum. The sporangia are scattered, 



