Notes . 
625 
' 
in the ontogeny of such a fern \ Hence the Aneimia type (which 
corresponds with that of a mature Polypodium ) may be regarded as 
the more specialized type among the Schizaeaceae , and Lygodium 
(which corresponds in structure with the base of the stem of Poly- 
podium) as the more primitive type. 
The Gleicheniaceae and Hymenophyllaceae also include forms with 
a solid central mass of xylem, but differing in some details from 
Lygodium . The protoxylem is well-marked and composed of annular 
and spiral elements in both orders. Gleichenia is mesarch and closely 
resembles the fossil genus Heterangium. 
In the Gleicheniaceae the only advance on the Lygodium type is 
found in Platyzoma (a sub-genus of Gleichenia :), in which there 
is a ring of xylem surrounding a central pith 2 , as in Schizaea , but 
differing from the latter plant in having an inner endodermis. 
In the larger species of Trichomanes there is a solid xylem-mass, 
but with a group of parenchyma in connexion with the one or two 
protoxylems, which are more or less centrally placed. In Hymeno- 
phyllum the corresponding parenchymatous mass is large in proportion 
to the amount of xylem. In the smallest species of Trichomanes the 
stele of the rhizome takes the form of a collateral bundle. The 
protoxylem of Trichomanes spicatum , unlike the other species examined, 
resembles that of the Schizaeaceae . 
The solid stele may be regarded as primitive, the Aneimia type 
being derived from it by the following steps : — 
1. Solid central xylem-mass surrounded by phloem, &c. 
2. Ring of xylem surrounding a central pith. 
3. Ring of xylem with internal phloem, endodermis, and pith. 
4. Ring of separate bundles formed by the breaking up of the 
above vascular ring, owing to large leaf-gaps. 
The Aneimia type thus explained would not be polystelic, in the 
morphological sense of the word, but the separate bundles would 
represent peripheral parts of an originally solid stele, in which the 
central part has been replaced by parenchyma, additional pieces 
of phloem and endodermis having been differentiated to complete 
the concentric bundles. 
The full results of this investigation will be published subsequently. 
L. A. BOODLE, Kew. 
1 Leclerc du Sablon, Annales des Sci. Nat., Bot., ser. vii, t. xi, 1890. 
2 Poirault, Ann. des Sci. Nat., Bot., ser. vii, t. xviii, 1893. 
