160 THE MARATTIALES 



III. THE OLDER SPOROPHYTE. 



The vascular system of the adult sporophyte in the Marattiaceae is extremely 

 complex, especially in the larger species of Marattia and Angiopieris. In Dancea 

 and Kaulfussta it is simpler, but in these also the arrangement of the bundles in the 

 adult stem is by no means easy to trace. A thorough study of the condition in the 

 early stages of the sporophyte is therefore specially important for understanding 

 the much more complex arrangement of the bundles in the older plant. 



In view of the conditions that we have found to exist in the Ophioglossacea?, 

 and particularly the nature of the vascular system in the young sporophyte of 

 Ophtoglossum moluccanum, a careful reinvestigation of the developmental history- 

 of the vascular system in the young sporophyte of the Marattiaceae, especially the 

 simpler and presumably more primitive genera Dancea and Kaulfussia, was very 

 much needed. To this end series of sections were made of young sporophytes of 

 both of the latter genera, ranging from individuals in which the second leaf was 

 still undeveloped to those in which a dozen or more leaves had been formed. These 

 series were fairly complete and made it possible to trace quite satisfactorily the evo- 

 lution of the vascular system in the young sporophyte of both Dancea and Kaulfussia. 

 Brebner (Brebner 3) has given an accurate account of the distribution of the bundles 

 in the young sporophyte of Dancea stmphcifolta, which agrees quite closely with the 

 arrangement of the bundles as I have found them in the species studied by me. 

 Jeffrey (Jeffrey 3) has described and figured a few specimens of D. alata (:), but 

 his material was too incomplete to make the study at all satisfactory. 



The available material of Marattia was much less complete, although a number 

 of stages were secured. Farmer has made an exhaustive study of the vascular system 

 in the young sporophyte of Angiopteris (Farmer 3), and an extended study of An- 

 giopterts did not seem necessary, therefore, except for a study of the early stages to 

 determine the origin of the vascular bundles. All of the writers mentioned con- 

 cerned themselves almost exclusively with the fully developed bundles, beginning 

 their study at the base of the stem and working upward. No attempt was made to 

 follow out the development of the vascular bundles from the meristematic region 

 of the apex and proceeding downward, a method of study which we think would 

 have materially modified the conclusions drawn by these observers in regard to the 

 relation of the different parts of the vascular system. 



In my studies as to the origin of the vascular system in the young sporophyte 

 of the Marattiaceae the course of the bundles has been carefully followed in series 

 of microtome sections, passing downward from the apical meristem to the base of 

 the sporophyte, where the axial primary bundle passes into the primary root. These 

 series of transverse sections were then compared carefully with series of longitudinal 

 sections of young plants of approximately the same age, and in this way a clear 

 conception was obtained of the arrangement of the vascular system within the stem 

 of the young sporophyte. 



THE DEVELOPMENT OF THE VASCULAR SYSTEM IN DAN^A. 



Especial attention has been given to the development of the vascular system in 

 Dancea and Kaulfussia, as these have received less attention than Marattia and 

 Angiopteris, and moreover are probably more primitive forms whose structures have 

 departed less from the ancestral type than those of either Marattia or Angiopteris. 



A longitudinal section of the young sporophyte of Dancea jamaicensis at the 

 period when the root is just about to emerge is shown in fig. 121, A. The root in 

 this species, as in D. simplicifolia, described by Brebner, is the first organ to appear 



