AND THEIR BEARING ON STELAR THEORIES FOR THE FERNS. 
731 
Osmunda regalis has been studied in the sporeling stages by Leclerc du Sablon (48), 
Jeffrey (33), G-wynne -Vaughan (27), and Sinnott (55), while Faull has provided 
the facts of sporeling structure for Osmunda cinnamomea (23). Sew are and Fore 
have performed a like service for Todea (54). 
Brebner (12), Charles (17), and Farmer and Hill (21) have described the 
sporeling structure of members of the Marattiacese ; while Lang has studied in 
detail certain of the Ophioglossacese (43), (44), (45), (46), (47). The facts for 
Alsophila have been described by Gwynne-Vaughan (25), for Doodia aspera by 
Chaneler (16), and for Pteridium aquilinum by Leclerc eu Sablon (48) and Jeffrey 
(33). All these, with the records of adult structure for a wide range of Ferns 
(see Bibliography), may easily be freed from the theoretical statements which cling 
around them. When this is accomplished, they are easily brought into line with 
the stelar facts recorded in these pages, and are most reasonably interpreted as 
illustrative of a process of static change of procambial elements by which stelar 
changes are affected. On this view it is held that the sum of the .ontogenetic 
evidence so far obtained for the Ferns shows that medullation and the solenostelic and 
dictyostelic states arise in the ontogeny entirely by intrastelar readjustment in 
which change of procambial destination is mainly operative. 
The object of the present memoir is to provide structural facts, but the meaning 
of stelar change will be dealt with latter. A list of the publications which appear 
to bear most directly on the subject of stelar development is appended. 
Summary. 
1. The object of this memoir is to provide the ontogenetic facts of stelar 
development for a number of Ferns. 
2. The sporeling structure of Schizsea malaccana is first dealt with. From 
serial sections it is concluded that the pith is of intrastelar origin. 
3. A number of incomplete adult stems of Schizsea dichotoma have been 
examined in serial sections, and the stelar structure reconstructed. From these it 
is concluded that this species has a medullated protostele, the medulla being of purely 
intrastelar origin. Endodermal pockets in this species are held to be intrastelar 
structures which arise by change of procambial destination within the stele. 
4. The ontogentic progression from protostely to solenostely is described for 
Gleichenia pectinata, Loxsoma Cunninghamii, and Acrostichum aureum , and the 
evolution of the Lindsay a type of stele is traced in Lindsay a adiantifolia. It is 
held that in these, medulla and inner phloem are of purely intrastelar origin, and 
that the inner endodermis and solenostelic structure of the adult stele of the former 
species arise by purely static change of quality of procambial elements as the apex 
of the stem advances. There is no evidence of intrusion of cortical tissues into 
the stele during medullation. 
TRANS. ROY. SOC. EDIN., VOL. LII, PART IV (NO. 28). 
113 
