1884.] On the Most Widened Lines in Sun-spot Spectra. 443 



daceoe that these exceptional cases occur. In the young leaves of 

 Todea superb a and of Osmunda cinnamomea it was found that the apex 

 is occupied by a well-marked, three-sided, conical, apical cell, from the 

 three sides of which segments are cut off in regular succession, as at 

 the apex of the stem of Equisetum. The apical cell is so placed that 

 one side faces the ventral side of the leaf, while the remaining two 

 sides are obliquely disposed witli regard to the dorsal side of the leaf. 

 No clearly marked marginal series of persistently active cells have 

 been found giving rise to the pinnae, as is stated to be the case for the 

 typical ferns. Further, there appears to be no strict relation between 

 the points of origin of the pinnae and the segments cut off from the 

 apical cell. The pinnae arise in acropetal order. 



In itself no great importance is to be attached to the difference 

 between a three-sided and a two-sided apical cell. For example, it 

 has been clearty shown in a paper by Treub, on the vegetative organs 

 of Selaginella Martensii, that the two forms of apical cell are to be 

 found on different shoots of the same species. But in the case of the 

 leaf of the fern, the whole development, as described by Sadebeck and by 

 Ruy, is so closely connected with the existence of a two-sided cell that 

 a departure from that arrangement is to be regarded as of more 

 importance than would otherwise be due to it, and it appears to me to 

 supply an intermediate step towards the more complex leaf of the 

 Marathacece and Cycadece. 



Finally, it is believed that this is the first described case of a clearly 

 marked, three-sided, apical cell occurring in the leaf of any plant. 

 Holle asserts that there is a wedge-shaped apical cell at the apex of the 

 leaf of Angioptris, and describes it as being " of irregular cross- 

 section." My own observations on this point, which will shortly be 

 described in detail, show that there is no single, functionally active, 

 apical cell in the leaf of Angiopteris evecta. 



III. " On the most Widened Lines in Sun-Spot Spectra. First 

 and Second Series, from November 12, 1879, to October 15, 

 1881." By J. N. Lockyer, F.R.S. Communicated to the 

 Royal Society at the request of the Solar Physics Com- 

 mittee. Received February 22, 1884. 



(Abstract.) 



A preliminary report by Mr. Lockyer, written before the reduction 

 of the observations given in the present paper was complete, was 

 read to the Royal Society on December 15, 1881, and printed in the 

 Proceedings (vol. 33, p. 154). In the present paper the author 

 describes the plan of the observations and of their discussion, and 

 presents some general conclusions. 



