CONNECTION OF THE BUNDLE-SVSTEMS. 313 



petiole. The single thread-like bundle, which enters the narrow base of the branch, 

 is inserted, in the first-named plants, at the lower margin of a foliar gap of the 

 stem ; in the specimen of Alsophila investigated several bundles are thus inserted, 

 each of which passes into one of the numerous shoots which arise round the base of 

 one leaf. The bundle of the lateral shoot of Struthiopteris has the same point of at- 

 tachment as in Aspidium cristatum; it is not thread-like, but has the shape of a 

 plate with a channel-like external groove, which gradually widens as it passes from 

 the point of attachment, and closes up to form a tube opening obliquely outwards and 

 downwards. Through the tube and channel the pith of the lateral shoot has con- 

 tinuous connection with the parenchyma of the main shoot, while where the bundles 

 are filiform at their point of origin this continuity does not exist. The lateral shoots 

 seated on the petiole in Aspidium Filix mas have as a rule the same thread-like 

 insertion of the bundles on one bundle of the petiole. More rarely the bundle-system of 

 the lateral shoot arises as three bundles from so many bundles of the petiole, or directly 

 as a tube filled with pith from the margin of a gap in a widened band-like bundle of 

 the leaf. Finally, in a species named as Diplazium giganteum, Stenzel found this 

 latter form of insertion in the branchings arising from the stem below the leaves : 

 each branch has its own small gap in the network of bundles of the stem, from the 

 margin of which arises the tube-like system of the branch. 



In the Ferns and Rhizocarps with elongated stems bearing two rows of leaves, 

 and with lateral shoots arising from the stem, not from the petiole, when there is a, 

 simple axile bundle present, there is naturally an insertion of the bundle which 

 passes to the lateral shoot on that which traverses the main shoot. In the Marsilia- 

 ceiB with a tubular bundle, that which enters the branch passes directly off in a 

 tubular form from the margin of a corresponding gap in the tubular bundle of the 

 main axis, through which gap the pith of the two axes is continuous. 



In the Ferns with clearly marked upper and lower bundles (see above, p. 287), 

 in most of the described cases ^, the bundle-system of the lateral shoot is united, as 

 in those ferns with leaves in many rows, into one bundle, which arises from the next 

 lower transverse bundle separating the foliar gaps : it usually has the form of a 

 channel open towards the pith. This is the case in Aspidium albopunctatum, coria- 

 ceum (comp. Fig. 135, p. 287), Acrostichum Lingua, brevipes, most Davallias, and 

 other above-named species, on the details of which Mettenius' description must be 

 referred to. According to Trdcul's investigation'', however, it appears that in A. 

 coriaceum the bundle passing to the branch is inserted both on the transverse and 

 on the lower bundle, at the angle between the two. Among the Davallias some 

 species (D. stenocarpa, divaricata) differ from the rest, inasmuch as a closed transverse 

 bundle limiting the foliar gaps is absent, but in its place, and in the direction which 

 it has in other species, two bundles run, the one arising from the upper, the other 

 from the lower bundle ; both converge obliquely towards the apex, and enter the 

 lateral shoot as upper and lower bundles without coming into contact. The arrange- 

 ment in D. chserophylla described by Mettenius is more irregular still, but should 

 be placed in this category. 



? Mettenius, Angiopteris, p. 546. ' Ann. Sci, Nat. 5 ser. torn. XII. p. 242. 



