XI] 



HAIRS AND SCALES 



199 



as seen in Matonia (Fig. 185, i). Very striking bristles of this type are found 

 in Zygopteris : they are attached by a narrow base, and are transversely 

 septate, while each segment may divide by radial cleavages. In other cases 

 these secondary walls may run parallel to one another, and a flattened scale 

 is the result. Thus Zygopteris shows in this, as in certain other features, 

 interesting signs of advance, though it is itself an early fossil, the affinities 

 of which are certainly primitive. 



A very curious structure is presented by the so-called " equisetoid " 

 hairs oi Botryopteris forensis, figured by M. Renault. They are borne on the 

 petiole. An examination of them in slides belonging to Dr Kidston showed 



Fig. 186. Glandular hairs, 

 which are alike on sporo- 

 phyte and gametophyte of 

 Notholaenatrichomanoides. 

 a = margin of cotyledon : 

 b — apex of prothallus. 

 (x85.)l 



Fig. 187. "Equisetoid" hairs oi Botryopteris forensis, Autun. 

 a, seen from without, b, seen in optical section ( x 82). Kidston 

 Collection, slide 182 1. To the right a similar hair ( x 164). It 

 is seen in obliquely tangential section, and shows in its upper 

 part the sinuous margins of the septa: below the septa are 

 seen in section, the middle of each being plane, and the 

 margins sinuous. Kidston Collection, slide 1820. 



that they are relatively large stiff hairs, transversely septate, and each is seated 

 on a multicellular emergence projecting from the surface of the petiole, in 

 the same way as in some species of Gleichenia and in the Cyatheaceae. 

 The " equisetoid " character arises from the fact that the margins of the 

 transverse septa are thrown into deep and rather regular corrugations, with 

 the result that upturned processes of equivalent size, each appearing to have 

 protoplasmic contents, are seen seated at the upper limit of each lower cell 

 just below the septum, but not segmented off from it. These processes inter- 

 lock with similar downward processes from the upper cell. Each septum of 

 the hair being thus frilled, their characteristic appearance follows (Kidston 

 Collection, slides 1818, 1820, 1821, Fig. 187). Increased mechanical strength, 



