The structure & development of the mosses and ferns (Archegoniatae) . of ratherlarge cells, within whichlies the phloem, whichcompletely surrounds thexylem, as in the sieve-tubes in thisspecies form a singlecircle just inside the peri-cycle, but according toGibson are absent op-posite the protoxylem. Fig. 262.—Cross-section of a fully-developed stem oi S. Kraussiana, showing the two vascular bundles sus- rle StatCS tnat tnCre IS pended in the large central lacuna by means of the Kiif p ^incrlp DTOim Ctftrabeculae (J), X 75; B, a single vascular bundle, & 0 Jr X450 ; X, X, scalariform
The structure & development of the mosses and ferns (Archegoniatae) . of ratherlarge cells, within whichlies the phloem, whichcompletely surrounds thexylem, as in the sieve-tubes in thisspecies form a singlecircle just inside the peri-cycle, but according toGibson are absent op-posite the protoxylem. Fig. 262.—Cross-section of a fully-developed stem oi S. Kraussiana, showing the two vascular bundles sus- rle StatCS tnat tnCre IS pended in the large central lacuna by means of the Kiif p ^incrlp DTOim Ctftrabeculae (J), X 75; B, a single vascular bundle, & 0 Jr X450 ; X, X, scalariform tracheids ; j, s, sieve-tubes. prOtOXylcm clcmentS here, but my own ob-servations lead me to think that there are two, as Russowaffirms is the case. The origin of the protoxylem wasnot traced, but the appearance of the mature bundle in thespecimens examined (Fig. 263, B) points to this protoxylem is made up of small spiral and annulartracheids, the metaxylem (secondary wood) of larger scalari-•^ Strasburger (7), p. 457. - Gibson (2), p. XIV L 499 form elements, as in Lycopodiiini. The sieve-tubes have delicatewalls and numerous, but poorly developed, sieve-plates upontheir lateral walls. While in the main the anatomical characters are essentiallythe same in all species examined, there arc a number ofdifferences to be noted/ Thus the stem may be monostelic(5. Martensii), bistelic (5. Kraussiana), polystelic (5. Icevi-ata). In the former species the presence of silica in theinner cortex has been demonstrated bv Strasburt/cr, andGibson - has shown the same thing in other species. In thisspecies, too, besides the simple trabeculse found in S. Kraussiana, £• ^ C
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
