XXXVIl] 



LINDSAYA 



31 



LiNDSAYA Dryander, 1793 



Lindsaya is a large genus, distributed over both hemispheres, with some 

 90 species as now reduced. Sir W. Hooker enlarged it by including as sub- 

 genera various Ferns now held as constituting substantive genera. The 

 rhizome bears superficial scales, and it contains a type of stele that is 

 characteristic of the genus, and bears its name (Fig. 600). It has been fully 

 described and discussed in Vol. I, p. 146, and it may be held as a general 

 character of the genus (Studies VII, Ann. Bot. XXXII, 1918, p. 13). The leaf- 

 trace is undivided: thus the whole vascular system is relatively primitive, 

 and its retention by Ferns which in other respects show advance was probably 

 promoted by the small size of the wiry rhizomes. 



Fig. 600. Transverse section of a stele of Lindsaya 

 linearis Swartz, showing the characteristic structure 

 with the central phloem included in the otherwise solid 

 tract of xylem. G.-V. collection, slide 992. ( x 125.) 



Fig. 600 his. Outlines of transverse 

 sections of the rhizome in Lindsaya and 

 Odontosoria, all drawn to the same scale. 

 The stele in each is shaded. The central 

 pith is clear. 



I = Lindsaya clavata, stelar diameter 

 •5 mm. 

 \\=L. trapeziformis, stelar diameter 

 •9 mm. 

 \\i — Odontosoria actdeata, stelar dia- 

 meter rSmm. 

 IV = O. fttinarioides, stelar diameter 



2'2 mm. 

 V= 0. retttsa, stelar diameter 3"omm. 



The incidence of the size-factor in relation to the structure of the rhizomes of the genera 

 Lt?idsaya, Odontosoria., and Diellia is illustrated by actual measurements taken on the 

 longer axis of the elliptical transverse section (Fig. 600 bis). In L. clavata with a measure- 

 ment of "5 mm., and in L. trapesifo7'mis of -9 mm., the Lindsaya-type of stele is seen. In 

 Odontosoria acideata with a stelar diameter of r8 mm., there is solenostelic structure with 

 a small central column of pith: in O. fumarioides with a diameter of 2"2 mm., the pith- 

 column is larger : and again it is of larger size still in O. retusa and Diellia falcata, each 

 with a measurement of approximately 3 mm. Thus the larger steles are consistently 

 solenostelic, while the smaller have the Lindsaya-'iXxnQ.X.mt.. The conclusion appears to be 

 that while Lindsaya retains permanently in its smaller rhizomes the state passed through 

 rapidly in the ontogeny of these and many other Ferns, the larger types pass on to the full 

 solenostely characteristic of so many rhizomes of larger size. 



