developmh;nt of the ostrich fern. 43 



but colorless protoplasm. The first to be transformed into permanent tissue are situ- 

 ated nearl}' in the center of the axial bundle in the base of the stolon. A number of 

 the cells of the procambium develop narrow transverse pits upon their walls, thus form- 

 ing a mass of short scalariform traeheids, from which the formation of trachearj' tissue 

 proceeds, following lines nearly parallel with the circumference of the ]:)undle. Sometimes 

 a complete circle is formed, sometimes they extend hardly more than half-way round. 

 The secondary tracheids are broader, l)ut not very long, and often with the lateral walls 

 somewhat sinuous. Their walls develop jierfect scalariform martings. 



In the two bundles found higher up, formed by the division of the plerome cylinder iuto 

 two unequal parts, much the same process takes place, the tracheary tissue beginning with 

 small scalariform tracheids near the center of the bundle, or sometimes toward one side, 

 and the sul)sequent ones are formed within, and also towards the sides. 



In the earlier formed parts of the stolon the bundle undergoes little further change ex- 

 cept that a sheath is foruied about it, and it is dilUcult to say whether some of the cells 

 represent the parenchjana or sieve-tissue of the more perfect bundle of the main stem. 



Just before the stolon appears above ground, the internodes become very much short- 

 er and the leaves, instead of being scale-like, assume the character of foliage leaves. 

 The young leaves are crowded together so that the end of the stolon is much thicker 

 than its subterranean portions. In the cases observed, there were usually two fronds de- 

 veloped above ground almost simultaneously, differing' so nmcli in appearance from the 

 later ones that, were their origin unlvuown, they would not be recognized as belonghig to 

 the same species as the mature fronds. Their pinnae arc much fcAver, and less crowded; 

 the lobes less deeply cut, and their margins somewiiat crenate; the whole frond looking 

 nuich like the earlier ones of the germ-plant. Sometimes these appear to l)e the only 

 leaves developed the first season, but in others later ones were formed, which, though small, 

 had all the characteristics of the pei'fect leaf. The plant is now, in everything but size, 

 complete, and soon becomes severed from the i)arent plant by the decay of the base of 

 the stohm, thus becoming independent. 



In one case a young branch was observed upon a stolon that had recently appeared 

 above ground; this appeared to be developed, not as an adventitious bud, as in the case 

 of the stolons themselves, but in the same way as a leaf, seeming to have taken the })lace 

 of one of them. Its fibro-vascular bundle was continuous with that of the stem, which 

 was still imdeveloped, none of the i)ermanent tissues having yet appeared. The end of 

 this branch had developed the rudiments of two leaves and was in all respects like the 

 end of any stem. Both stem and leaves had already developed scales. 



Section VI. The Root. 



The roots are produced in abundance from and near the bases of the okler leaf-stalks. 

 Each jirimar}^ root develops numerous secondary ones that are ari-anged in tAvo i-anks 

 in opposite sides of the main one. In all but the youngest parts the root is co-s'ered with 

 a sort of dark browTi cortex, formed by the remains of the ex^idermis and the underlying- 

 cells. 



The development of the main roots can best be seen on the earlier aerial leaves of a 

 stolon, as it is less difficult to make satisfactory sections than in the thicker mature stems. 

 They arise from the bundle-sheath of the stem-bundle before any permanent tissue is de- 



