194 



MORPHOLOGY. 



144 



but even these are very far from being complete : there is no reference 

 whatever made here to the first origin of the new cells. There is, how- 

 ever, some importance to be attached to the observation, that there 

 appears in the proembryo an ovate corpuscle free at both ends, which 

 naturally, therefore, remain capable of propagation in opposite directions, 



by which the morphological distinc- 

 tion of stem and root (fig. 144.) first 

 appears in the series of vegetable 

 forms. Our knowledge regarding 

 the extensive history of develop- 

 ment is, however, very deficient, 

 and we need far more exact and 

 fundamental investigations on the 

 relation of stem and leaf, as well as 

 on the formation of the furcated 

 divisions of the stem and the germi- 

 mation, since without such observa- 

 tions little that is of importance can 

 be said upon the subject. 



The morphology of leaf and stem, 

 as far as it is applicable to Ferns, 

 must be derived from the Phanero- 

 gamia ; the term frond (frondes), as 

 applied to the leaves, is here quite 

 superfluous. 



We know, as yet, nothing of the signification of the accumulation of 

 pulverulent cells * in the axilla of tropical Ferns, which Von Martius once 

 asserted, without any reason, to be antheridia ; they may perhaps be 

 wholly analogous to the lenticels of Phanerogamia (see below). 



108. A. In all cases spores are formed in the tissue of a true 

 leaf, which either appears wholly unchanged or is attenuated by the 

 non-development of all or of the most superfluous part of the 

 parenchyma around the principal nerves : I call it the spore-leaf 

 (sporophyilum). Where it differs but little, or not at all, from the 

 ordinary leaves, it shows upon the back, or on the margin, differently 

 formed, scattered accumulations (sori) of sporocarps, which are 

 generally entirely or partially covered by a definitely formed fold of 

 the epidermis (the indusiuni). The several sporocarps are commonly 

 fastened to a somewhat elevated mass of cellular tissue, which 

 appears as a short pedicle or as a seam, more seldom as an elongated 

 pedicle (as, for instance, in Hymenophyllum), and they are formed 

 in the following manner : From the parenchyma of the leaf (that 

 is, from those pedicles) there rises a cell, which soon separates into 

 two, one cylindrical and one spherical. In both, new cells are 

 formed ; in one they form the pedicle of the sporocarps, the others 

 fill the spherical terminal cell (capsula) ; the most external consti- 



* Compare H. Mohl, De Structura Filicum Arborearum, Monach. 1833, p. 7. 12. 



144 Pteris spec. B, Germinating plant : a a, the two lobes of the proembryo ; b, the 

 first leaf of the young plant ; c, the root. A, A longitudinal section of a somewhat 

 earlier germinating plant : , lobes of the embryo ; 6, first leaf of the plant ; c, root ; 

 d, terminal bud. 



