LYCOPODIACEM. 



417 



As to the Forms of Tissue in Lycopodiaceae\ it may be remarked that the fibro- 

 vascular bundles which penetrate the stem belong exclusively to it or are ' cauline.' They 

 may be followed in the procambial condition close beneath the apical cell to the apex 

 of the stem and the youngest leaves. This I have found to be the case in Selaginella 

 inaqiialiforia and Martensii and in Lycopodium Chayyicecyparissus ; and, according to Nageli, 

 the fibro-vascular bundle of Psilotum is also cauline, since no branches pass from it 

 into the leaves (Nageli, Beitr. p. 52). Proceeding downwards from the apex of the 

 stem, it is seen that the leaves which are already more developed each form a pro- 

 cambial bundle which applies itself to that of the stem. In the angle where they meet 

 the formation of spiral vessels begins, and advances downwards into the stem, outwards 



Fir., -ji I. —Transverse section of tlie stem of Sfla^inella inc^quali/olia (X150). 



into the leaf. In their procambial origin part of the fibro-vascular bundles of Lyco- 

 podium and Selaginella are therefore cauline, and part foliar; but the formation of 

 the first spiral vessels takes place as if they were 'common' {cf. Equisetum). The 

 first spiral vessels of the cauline bundle arise near its edges; the formation of the 

 wider vessels, which are thickened in a scalariform manner, proceeds from them in a 

 centripetal direction as seen in a transverse section. This occurs in different ways ac- 

 cording to the nature of the cauline bundle, which is very simple in Selaginella denticulata 



^ On the development of the tissues in the roots, especially on the eccentric position of the 

 fibro-vascular bundles in those of Isoetes, compare NageH and Leitgeb, Beitrage zur wissensch. 

 Bot. 1867, Heft IV. 



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