SUBGENERA AND SPECIES OF SELAGINELLA. 151 



geard (I.e.) has shewn that the primary axis of S. 

 Kraussiana has a similar structure, and I have found 

 that indications of the peculiarity are not wanting in 

 other species. Further researches which I hope soon 

 to undertake may result in shewing that the central 

 protoxylem in the primary embryonic axis is the rule 

 rather than the exception. The erect shoots of S. 

 spinosa are not greatly removed from the creeping 

 rhizome of S. Lyallii, for here also there occurs a 

 single cylindrical stele with protoxylems on its outer 

 border. The cylinder is however not hollow save in 

 the apical regions where the place of the metaxylem 

 is still occupied by procambium. 



3° S. Galeottei, Spr. The so-called bistelic species I 

 feel sure are to be derived from species with steles 

 like those of S. Lyallii, (where the leaves are in four 

 rows) by fusion of the protoxylems of adjacent leaf- 

 traces and feeble development of metaxylem, so that 

 two laterally placed steles result each with one proto- 

 xylem marginally situated. 



4° 8. Braunii, Bak. In this type the creeping axis, 

 differentiated from the erect shoots as in S. Lyallii, 

 is at first monostelic and then later bistelic, the steles 

 being dorsal and ventral, not lateral. The erect 

 shoots are however monostelic the two marginal 

 protoxylems arising from the dorsal and ventral steles 

 respectively. S. Braunii I consider as related to 

 S. Lyallii, although in the former the leaf traces have 

 fused into one cord on either side and the two cords 

 so formed have become connected by metaxylem. 



5° S. Oregana, Eat. In this species we have a transi- 

 tion between S. spinosa and the usual Selaginella 

 type, for here although the leaves are homophyllous 

 the stele is dorsi-ventral. 



