The structure & development of the mosses and ferns (Archegoniatae) . otyledon, and its nearly flatsurface is at right angles to theaxis of the latter. The secondleaf (L^) arises as a slight eleva-tion on the side of the stemdirectly opposite the the first it is multicellular,and its growth is entirely likethat of the cotyledon, whichit otherwise resembles in all re-spects. Almost as soon as theleaf is evident at all, a strand of procambium cells is formedrunning from the junction of the cotyledon and first root, andis continued into the second leaf as its plerome. The second ro
The structure & development of the mosses and ferns (Archegoniatae) . otyledon, and its nearly flatsurface is at right angles to theaxis of the latter. The secondleaf (L^) arises as a slight eleva-tion on the side of the stemdirectly opposite the the first it is multicellular,and its growth is entirely likethat of the cotyledon, whichit otherwise resembles in all re-spects. Almost as soon as theleaf is evident at all, a strand of procambium cells is formedrunning from the junction of the cotyledon and first root, andis continued into the second leaf as its plerome. The second root develops from the base of the second leafin the immediate vicinity of the common fibrovascular bundle,and is formed about the time that the leaf begins to group of cells here begins to multiply actively, and verysoon shows a division into the initials of the tissue systems ofthe young root. From this time the growth proceeds as inthe primary root, and it finally breaks through the overlyingtissues. The stem has no vascular bundle apart from the common. Fig. 154.—Longitudinal section of the secondroot, X525 ; //, plerome. IX MARATTIACE^E—ISOETACE^ 291 bundle formed from the coalescence of the bases of the bundlesfrom the leaves and roots. In all the later-formed leaves androots there is but a single axial bundle. In the leaves this isdecidedly collateral in form with the poorly-developed xylemupon the inner (upper) side. Except for their larger size, andtheir having usually four instead of two air-channels, the laterleaves resemble in all respects those first formed. The development of the young plant was not followedbeyond the appearance of the third leaf, but it probably in itslater history corresponds to /. lacustris. Here, according toHofmeister,^ the opposite arrangement of the leaves continuesup to about the eighth, when the |- divergence is replacedsuccessively by ^, |-, |-, y^g, and -^^, which is the condition inthe fully-developed sporophyte. Tlie Spor
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
