TABLE OF CONTENTS. XV 



CHAPTER XII. 



PAGE 

 ISOETES LACUSTRIS . . 336 



Importance of the study of the development of the Isoeteae in botanical 

 morphology, 336 ; peculiar phenomena in the growth of these plants 

 indicated by Von Mold, 336, 337 ; observations on the arrangement 

 of the fronds of young plants, by A. Braun, 337 ; structure of the 

 spore described by Mettenius, 337 ; Karl Midler's account of the 

 germination of Isoetes lacustris, and observations of Mettenius on the 

 same subject, 337 ; form and structure of the microspores of Isoetes 

 lacustris, 338, 339 ; Roper and Schleiden on the supposed presence 

 of carbonate of lime in the exosporium, 338 ; evolution of the spores, 

 339 ; formation of the prothallium, 339, 340 ; production of arche- 

 gonia, 340, 341 ; microspores of Isoetes lacustris, 341 ; production of 

 spermatozoids by them, 341 343 ; observation of Mettenius on the 

 slow motion of the spermatozoids, 342, note ; development of the 

 embryo, 843 345 ; production of the first leaf, 345, 346; develop- 

 ment of the scale, 347 ; formation of the sheath, 347 ; growth of the 

 primary axis, 347 ; formation of the first root, 348, 349 ; develop- 

 ment of subsequent roots, 350 355 ; experiments on the germina- 

 tion of spores, 351 ; arrangement of the leaves, 354 ; structure of the 

 stem in the germ- plant, 356; formation and development of cam- 

 bium, 356, 357; growth of bark, 357 358; formation of roots of 

 the second year, 358 360; ramification of the roots, 360; sub- 

 sequent growth of the plant, 360, 361 ; effect of the annual 

 renovalion of the cambial layer, 361, 362 ; scalariform arrangement 

 of cells in the leaves, 362 ; periodicity in the production of sterile 

 and fertile leaves in Isoetes, 362363; origin of the scales of the 

 leaves, 363, 364; production of the sporangia of Isoetes lacustris, 

 364367 ; spore-mother-cells, 365, 366 ; furrows of the underside 

 of the stems in Isoetes, 367; differences of growth connected with 

 the presence of one furrow or more under the stem, 367 370 ; re- 

 semblance of Isoetes in its mode of reproduction to the Conifers, 370 ; 

 spores of Isoetes favorable to the observation of the peculiar mode 

 of reproduction by macro- and microspores, 370, 371 ; distinction of 

 germination of Isoetes from that of vascular cryptogams with green 

 prothallia, 371 ; agreement of Isoetes with Lycopods, both in vegeta- 

 tion and fructification, 371, 372 ; annually renewed cambium-layer, 

 peculiar to Isoetes among vascular cryptogams, 372 ; general observa- 

 tions on the stem and roots of Isoetes, 372. 



CHAPTER XIV. 



SELAGINELLA ... . 373 



Growth of the end of the stem in species of Selaginella, with 2| 

 arrangement of leaves, 373376 ; formation of the leaves, 376 

 380; production of a flat cellular body (stipule) from the upper 

 side of the base of the leaf, observed by R. Midler, 378 ; structure 

 of the stipule, 378, 379 ; production of papillae at the margins of 

 the leaves, 378, 379 ; furcation of the apex of the stem, 380382 ; 



