188 FLORA OF LOWER COAL MEASUEES OF MISSOURL 



and complicated secondary or exogenous development.^ The examination 

 of the structure of certain dolomitized bolsters of LepidopMoios by Dr. 

 Potoni^^ shows that the two lateral appendages below the leaf scar in Lepi- 

 dodendron and LepidopMoios are the aerial termiiiations, beneath greatly 

 thinned bolster walls, of strands of thin-walled parenchjaiia cells, apparently 

 with intercellular spaces. These strands or ducts, whose function is 

 regarded hy Potonie as transpiratory, pass through the leaf scar by way of 

 the lateral cicatricules and correspond with the two similar tracts found by 

 Felix ^ in the cross section of the leaf of Lepidodendron selaginoides. Potoni^ 

 follows Stur* in designating the trace on the bolster above the leaf scar in 

 the Lepidodeiidrem as the "ligular pit," on account of its supposed homol- 

 ogy with the ligule of the recent SelagineUa. The propriety of this corre- 

 lation has, however, been doubted by a number of paleobotanists, among 

 whom is Mr. Kidston.^ 



Lepidodendron Bbittsii Ls. 



PI. LII, Figs. 1, 2; PI. LIII, Fig. 1; PL LIV, Figs. 1, 2. 



1879. Lepidodendron Briitsii Lesquereux, Coal Flora, Atlas, p. 11, pi. Ixiii, figs. 1,2; 



text, voLii(lS80), p. 368. 

 1883. Lepidodendron Brittsii Lesquereux, 13th Rept. Geol. Surv. ludiaua, 2, pl. xvii, 



figs. 4, 4&. 

 1889. Lepidodendron Brittsii Lx., Lesley, Diet. Foss. Peimsylvania, vol. i, p. 313, 2 



text figs. 



Stems of cousideralDle size, slightly rigid, freely branching at a rather 

 naiTOW angle in Ijoth equal and unequal dichotomies, the branches becom- 

 ino- slender, tapering slowly, flexuous, and plumose; bolsters contiguous, 

 rhomboidal-oval, acute both above and below, sometimes nearly one-half as 

 broad as long in the old stems, but generally fusiform, very slender, the 



'Detailed descriptions of the structure of a number of species may be found in the series of 

 memoirs published in the Philosophical Transactions of the Koyal Society, by the late Prof. W. C. 

 Williamson, or in tho painstaking- studies of Professors Renault and Bertrand. A very short resume 

 relating to the development of the Lepidodendroid stem was given by the author in Science, 1896, vol. 

 ill, pp. 751-759. 



-Anatomie der beiden "Male" auf dem unteren Waugenpaar uud der beiden Seitenuiirbchen 

 der Blattnarbe des Lepidodeudreeu-Blattpolsters: Ber. d. deutsch. hot. Gesell., vol. xi, 1893, Hft. 5, 

 pp. 319-326, pl. xiv. 



' Untersuchuugeu iiber den innereu BauWestfiilischer Carbon-Pflanzen: Abh. d. k. Preuss. Geol. 

 Landesanst., vol. vii, 1886, Hft. 3, pl. ii, fig. 3. 



■"Die Culm-Flora d. Ostrauer u. Waldeuburger Schichten : Abh. d. k.-k. Geol. Keichanst., vol. 

 viii, 1877, Hft. 2, p. 327 (231 j, pl. xxsvi (xix), fig. 1. 



Traus. Royal Society of Edinb., vol. sxxvii, pt. iii, 1893, p. 537. 



