STIGMARIA. 279 



tracheide as such with any certainty in the preparation which Renault most 

 kindly demonstrated to me; and he told me indeed that it could once be 

 more plainly seen. But apart from this I am chiefly impressed by the fact 

 that neither I nor any one else have been able to find anything of the kind 

 before or since in material from England, which has been examined over and 

 over 'again. And yet according to Renault these lateral roots occur fre- 

 quently all round the appendages; he says distinctly 1 : 'It seldom 

 happens that a transverse section through any part of a radicular appendage 

 does not disclose indications of the first beginning of a rootlet at one of the 

 three angles of the primary wood.' Unfortunately he gives us no more 

 precise information about these ' indications.' From these doubtful state- 

 ments he proceeds to the conclusion that the surface of these appendages 

 must show three vertical longitudinal rows of ' cicatricules.' That the 

 presence of these scars has never been ascertained by direct observation, he 

 attributes to their minuteness (they are sup- 

 posed to be only from one to two-tenths of a 

 millimetre in thickness), and to the insufficient 

 state of preservation of the specimens. 



Lastly, the point of insertion of the 

 appendages on the axis in Stigmariae shows 

 some further anatomical peculiarities (Fig. 36), 

 and it is Williamson again who has directed 

 his attention especially to this subject 2 . The 

 vacant space which separates the outer and FlG . 36 . stigma ficoides. Transverse 

 the inner cylinder from one another comes to bearing tL th two Appendages cut trough 



i ., j j 1 j.1 iU i. C longitudinally, above is the ring of wood 



an end quite suddenly exactly at the point of composed of numerous wedges. After 



, T . re -i Williamson (6), less than the natural size. 



attachment. It is cut off by a transverse 



diaphragm formed of stout tissue, and represents the portion of the 

 outer rind of the axis beneath the appendage. The diaphragm is 

 traversed by the trace-bundle, which, as it emerges to enter the appendage, 

 is still surrounded for a short distance by a sheath of the stout paren- 

 chyma which ultimately comes to an end in the inner cylinder. Hori- 

 zontal sections of the diaphragm-plate are seldom obtained ; the only one 

 which I find in my preparations agrees perfectly with the one which 

 Williamson has figured 3 . Within the stout plate of parenchyma is a weak 

 bundle-trace, which certainly belongs to the type of the second class de- 

 scribed above. In these specimens therefore the secondary growth in the 

 traces must have ceased while they were passing through the rind, if there 

 was any growth of the kind, a point which in the absence of transverse 

 sections of these specimens cannot be certainly proved. Analogy with the 



1 Renault (10), p. 30. Williamson (1), il, t. 31, f. 52, and (6), tt. 5, 6, 8, 10. 



s Williamson (6), t. 5. 



