1894.] On the Ascent of Sap. 3 



cells next below the actual epidermis. This feature occurs in many 

 recent roots. 



It is shown incidentally that the doubts expressed by Messrs. 

 Hick and Cash as to the identification of their " MyriopTiylloides " 

 with " Astromyelon " are unfounded. A section of the type-specimen 

 of " MyriopTiylloides " has been re-examined, and its structure is 

 shown to be identical with that of the other specimens of " Astro- 

 myelon" 



The numerous minute rootlets, associated with the larger roots, 

 have been carefully examined. Many of these rootlets are without 

 any pith, but they are in other respects identical with the typical 

 specimens, with which they are connected by an unbroken series of 

 intermediate forms. There are also instances in which rootlets are 

 found inserted upon the medullate roots. 



The conclusions at which the authors arrive are the following : 



1. The fossils hitherto described under the name of Astromyelon 

 Williamsonis are the adventitious roots of Calamites. 



2. Their structure is in all respects that characteristic of roots, as 

 is proved by the centripetal primary wood, the alternating strands of 

 primary wood and phloem, the endogenous mode of branching, and 

 the absence of nodes. 



3. The smallest specimens, with little or no medulla, represent the 

 finest branches of the same roots, of which the large medullate forms 

 are the relatively main axes. 



The paper is illustrated by micro-photographs from the actual 

 specimens, and also by camera-lucida drawings. 



II. "On the Ascent of Sap." By HENRY H. DIXON, B.A. 

 Assistant to the Professor of Botany, Trinity College, 

 Dublin, and J. JOLY, M.A., Sc.D., F.R.S. Received October 

 16, 1894. 



(Abstract.) 



Strasburger's experiments have eliminated the direct action of 

 living protoplasm from the problem of the ascent of sap, and have 

 left only the tracheal tissue, as an organised structure, and the tran- 

 spiration-activity of the leaf, wherein to seek an explanation of the 

 phenomenon. The authors investigate the capability of the leaf to 

 transpire against excessive atmospheric pressures. In these experi- 

 ments the leaf was found able to bring forward its water meniscuses 

 against the highest pressures attained and freely transpire. Whether 

 the draught upon the sap established at the leaf during transpiration 

 be regarded as purely capillary or not, these experiments lead the 

 authors to believe that it alone is quite adequate to effect the eleva- 



B 2 



