292 , ME. D. T. GWYXXE-VAUGHAN ON" THE 



common endodermis *, although this could not be decided from the young seedlings 

 examined by me. In the nodal regions, which, according to Trecul t, represent four 

 successive nodes Avith their internodes contracted to obliteration, the bundles of the two 

 inmost circles branch and anastomose in an extremely complicated manner, as has been 

 described by Wigand in the ' Bibliotheca Botanica,' vol. ii. Heft 11. 



It seems to me possible that the intense complexity of the arrangement of the bundles 

 in Victoria, Wymphwa, and l^wpliar may have been derived from a simpler structure 

 previously existent in a stem wdth longer internodes, as a result of the contraction 

 and elimination of these internodes in consequence of the adoption by the stem of 

 a rhizomic habit. 



Anatomy of the Seedling, 



The arrangement of the vascular tissue in the young seedling of Victoria regia is, on 

 the whole, very similar to that in the mature rhizome, but the limiting zone of the 

 central mass is more prominent, and is separated off from the irregular bundles lying 

 wdthin it in a much more decided manner, because the position of the inmost system of 

 horizontal tracheides which are usually present in the mature rhizome is here occupied 

 by a corresponding belt of parenchymatous cells. It becomes quite clear in the seedling 

 that the bundles which supply the leaf- traces are derived from the internal vascular mass, 

 whereas those which eventually supply the roots are derived from the limiting peripheral 

 zone. Passing further dow^n still in the seedling stem the central mass decreases steadily 

 in size, particularly with regard to its internal irregular constituents, so that the bundles 

 of the peripheral zone become relatively more conspicuous still. Nevertheless these also 

 decrease in number until a point near the insertion of the first leaf is reached where only 

 four of them remain. At this point also only a few of the tracheides of the internal 

 vascular tissue persist. Pinally the four peripheral bundles unite to form two, which 

 are placed in the epicotyl exactly opposite one another, so that their xylems are confluent 

 in the centre with the remains of the internal tracheides, if, indeed, any of these are still 

 present. Stating these facts from another point of view, it may be said that the transition 

 from the narrow epicotyledonary stele to the structure found in the mature stem takes 

 place in Victoria in a manner quite similar to the same proceeding in an ordinary 

 monostelic plant. The bundles of the epicotyledonary stele subdivide so as to form a 

 number arranged in a ring around a central pith. So, for some time at any rate, the 

 young seedlin-*, is undoubtedly monostelic, having a single central cylinder with a 

 common endodermis surrounding it; the presence of the latter being, under suitable 

 treatment, clearly demonstrable even so far up as the fourth leaf. But in Victoria regia, 

 above the insertion of the first leaf, this central cylinder at the same time undergoes 

 great modifications from the appearance in the medulla of an ever-increasing amount of 

 vascular tissue. Concurrently with this the central cylinder itself becomes more and 

 more expanded, irregular, and broken up, until in the mature rhizome its limits are quite 

 unrecognizable as such. 



* Bull. Soc. Bot. de Pr., vol. xxxiii. p. 75. f Ann. dee Sc. Nat., ser. 4, torn. i. p. 296. 



