Bower . — Shi dies in the Phytogeny of the Filicales . 477 
show the course of the marginal segmentation, and to demonstrate that the actual marginal cell 
directly forms the apex of the receptacle of the sorus. The upper (u) and lower (/) indusial flaps 
arise as superficial, that is intramarginal upgrowths, x 250. 
Fig. 12. i-vi. Successive transverse sections of a runner of Cibotium Barometz , from the 
insertion of the lowest leaf to its extreme base. For details see the text, x 2. 
Fig. 13. Photograph of a transverse section at the base of a runner of Cibotium Barometz , 
showing the ‘ Lindsaya ’ condition. 
Fig. 14. Transverse section of a petiole of Thyrsopteris elegans. x 2. 
Fig. 15. a, b, c. Successive transverse sections of a small runner of Thyrsopteris elegans. a is 
near to the base of insertion, and shows a simple solenostele, with the origin of a root ; b is higher 
up, and a medullary strand is seen within the solenostele ; c is again higher, and shows a leaf-trace 
given off, the leaf-gap nearly closed, with a thickening of the lip preparatory to giving off a 
compensation strand, x 6. 
Fig. 16. a , b. Successive stages in the development of a sorus in Saccoloma elegans , showing 
that the origin of the receptacle is strictly marginal and the individual flaps superficial. It is to be 
noted that the lower flap (/) takes precedence at first over the upper {u). x 250. 
Fig. 17. a, b. Successive stages in the development of a sorus of Odontosoria retusa, showing 
the marginal origin of the receptacle and the proportions as in Saccoloma. x 250. 
Fig. 18. A more advanced stage in the marginal sorus of Odontosoria retusa. u = upper, 
/ = lower indusium. The vascular receptacle bears the oldest sporangium centrally, i. e. it takes the 
position of the marginal cell, while other sporangia and hairs originate laterally, x 100. 
Fig. 19. Transverse section of a sorus of Odontosoria retusa of same age as Fig. 18, traversing 
it in a plane a , b, while the plane of Fig. 18 would correspond to the plane c, d. It is seen that 
the oldest sporangia form a linear series in a median position, x 100. 
Fig. 19 bis. Base of sporangium of Odontosoria retusa , showing the oblique annulus with its 
induration interrupted at the insertion of the stalk, x 125. 
PLATE XXXIV. 
Fig. 20. A single pinna of Lindsaya lancea, showing the furcate venation, and the sori fused 
laterally to form an almost continuous, apparently intramarginal series. Both upper and lower 
indusial flaps confluent, the upper forming the false margin of the pinna, x 6. 
Fig. 21. A small part of the marginal region of a similar pinna, showing an incomplete lateral 
fusion of the sori, which explains how the Lindsaya sorus was arrived at. To the left is an almost 
isolated sorus of the Saccoloma type. To the right a more complete fusion is seen, while vascular 
commissures connect the receptacles laterally. From a drawing by Mr. Thompson, x 70. 
Fig. 22. A sporangium of Lindsaya repens , (Bory) Bedd., showing the annulus as a continuous 
ring, but the induration of its cells is not continued beyond the insertion of the stalk, x 250. 
Fig. 23. A vertical section through a very young sorus of Davallia pentaphylla, showing the 
marginal segmentation leading up to the receptacle, which appears as a valley between the two 
indusial flaps. As before, the lower (/) takes precedence at first of the upper ( u ). x 250. 
Fig. 24. A similar section of the sorus of D. pentaphylla , but older. The lower indusium (/) 
has run out to a single layer of cells; the upper ( u ), which ultimately forms the false margin of the 
leaf, is more bulky, and shows signs of intercalary activity. The first sporangium occupies a central 
position on the receptacle, and a later one is seen laterally, thus indicating a gradate sequence, 
x 250. 
Fig. 25. A vertical section of the young sorus of Nephrolepis biserrata, (Sw.) Schott, showing 
the great inequality of the indusial flaps. The lower ip) is markedly intramarginal ; the upper ( u ) 
appears very definitely as a continuation of the leaf-surface, and has an active marginal segmentation, 
x 250. 
Fig. 26. a , b, c. Sporangia of Loxsoma, seen from three different points of view. For details 
see the text, x 100, 
Fig. 27. Photographic reproduction of the diagrams of Professor von Goebel (‘ Flora’, cv, Heft i, 
p. 41, Fig. 7). But his diagram (II) has been orientated afresh, in relation to the placenta {pi), 
and duplicated, so as to show the condition seen in G.fiabellata , where, seated upon the leaf lamina, 
is a sorus, with slightly raised receptacle or placenta {pi), and sporangia on either side of it. This 
is shown in Fig. 27 bis. 
