THE PINNA-TRACE IN THE FERNS. 361 



leaf) the supply to the basal pinnae was marginal, of the type seen in the supply to 

 the basal pinnae in Cystopteris montana. 



In a young plant of Asplenium bulbiferum, the supply to the basal pinnae in the 

 first leaf was marginal. The xylem formed a narrow plate, its long axis at right 

 angles to the radius of the stem of the plant. From the margins of this line of 

 tracheides the pinna-trace was simply nipped off. 



In a young plant of Asplenium lunulatum, Sw., sub-sp. erectum, Bory, the supply 

 to the basal pinnae in a very early leaf was marginal. In the ninth or tenth leaf the 

 supply was also marginal to the basal pinnae. In the earlier leaf the group of 

 tracheides was arranged in a compact mass, wide and slightly hollowed on the 

 abaxial side and with two diverging extensions towards the adaxial corners. In the 

 later leaf the abaxial portion had two little projections, each composed of only a 

 few tracheides, while the adaxial extensions were much longer than in the earlier leaf. 

 The axis is dictyostelic and the leaf-trace departs from the strands subtending the 

 leaf-gap at a point where the two strands almost meet. The leaf-trace is single, 

 though made up of two portions of xylem, coming each from one limb of the 

 dictyostele. There is a common endodermis round the two portions of xylem and 

 their surrounding phloem. 



After the pinna-trace has left the petiolar bundle it develops differently in 

 different Ferns. 



Traces like that of Loxsoma are fully formed by the time they pass into the pinna. 



Gleichenia, Osmunda, Todea, Hymenophyllum, Trichomanes, Balantium culcita, 

 Dicksonia fibrosa, Histiopteris incisa, Hypolepis tenuifolia, the Cyatheaceae all have 

 this type of pinna-trace. 



Ferns with a " broken " leaf- trace (e.g. Diacalpe aspidioides) give off the pinna- 

 trace as a " signet-ring," then break it into two in the pinna, and nip off the other 

 strands from the aporachial ends of these two. 



In Davallia pallida the pinna-trace passes into the stalk of the pinna as a dorsi- 

 ventrally constricted mass of xylem enclosed in phloem (PI. XXXIII. fig. 2). The 

 xylem is wider in the centre of the pinna-trace than at the edges, where the margins 

 are slightly curved towards the prosrachial side of the stalk. A short distance out 

 into the pinna-stalk there appear suddenly in the phloem on the aporachial side, first 

 a single tracheide and then a small group, two or three in number (text-fig. 6, b). 

 These are quite separate from the main set of tracheides of the pinna-trace, but as 

 they increase in number the tracheides of the main trace extend towards them, and 

 presently the two sets join (text-fig. 6, c). We have then a pinna-trace of triangular 

 outline, the large amount of tracheides— and these greater in size of lumen than the 

 others — in the central position, the margins being composed of a narrow set of small 

 tracheides. Further out into the pinna the aporachial side of the group of tracheides 

 becomes widened out on the peripheral face, so that there are two triangular groups 

 attached to each other by the apices of the triangles (text-fig. G, d). A little further 



