62 
F. IV. Oliver. 
As I have already said, this sporangium suggests a comparison 
with Botryopteris. I turn therefore to the Botryopterideae in the 
first instance with a view to determining how far the ascertained 
facts of their sporangial structure favour a reference of my 
sporangium to this group. 
Zygopteris, Corda. Here the sporangium is large, being 
2.5 mm. long by 1.3 mm. across its longer transverse diameter. 
The wall in Renault’s figures 1 consists of a single cell-layer of well 
preserved cells with two indurated bands (the annulus) passing 
down the two opposed faces. A second layer or membrane is 
usually shewn retracted from the wall and enclosing the spore 
mass; Grand’Eury 2 figuring a similar form ( Schizostachys frondosus) 
represents the wall as of several layers. 
Solms-Laubach 3 conjectures “ that the inner layers were 
destroyed in Renault’s specimens, and his figures show a sac-like 
envelope inclosing the spores, which I can only suppose to be a 
crushed cell layer.” D. H. Scott 4 in reproducing Renault’s figures 
regards the sac-like envelope as a possible tapetum. A point of 
great interest is recorded by Renault 5 in the statement that the 
pedicel of the sporangium in Zygopteris is traversed by a flattened, 
bi-polar, vascular band which extends to the base of the sporangium, 
being accompanied by a tissue which he regards as phloem. The 
spores of Zygopteris have a diameter of .08 mm. 
Botryopteris dubius , B.R.—The sporangia of this plant have 
been fully described and figured by Renault 6 . The walls of the 
sporangia were relatively massive and consisted of several series of 
cells. In the best preserved specimens two layers were distin¬ 
guishable in the wall:—an outer layer three or four cells deep 
limited externally by an epidermis; and an inner, some three cells 
deep, the elements of which were elongated in the sense of the chief 
axis of the sporangium. There was an indurated band (annulus) 
passing down one side of the sporangium. The dimensions of the 
sporangium and of the spores are essentially the same as those 
’Ann. des Sci. Nat. (Bot.), ser. vi., vol. iii., pi. i., figs, r to 3. 
2 Flore carbonifere du d6p. de la Loire, p. 201, and tab. xvii., d and d 1 . 
This author comments on the thickness and complexity of the 
wall, which he states to be formed of an outer cellular and an 
inner fibrous layer. He suggests a comparison with the 
pollen-sacs of Cycns. 
3 Fossil Botany, ling. Edu., 1891, p. 150. 
4 .Studies in Fossil Botany, p. 287. 
‘Flore fossile d’Autun et d’Epinac, pt. ii., p. 43. 
'Ann. des Sci. Nat. (Bot.), ser. vi., vol. i., pi. x., fig. 24 and pi. xi., 
figs. 25, 26, 27. 
