On the Prothalli of Ophioglossum pendulum (Z.), &c. 405 



lengths. The prominences visible during totality had comparatively 

 simple spectra, the greatest number of lines recorded being 36. 



The heights above the photosphere to which many of the vapours 

 can be traced in the photographs are tabulated and compared with 

 the results obtained in 1898; the two sets of figures are sufficiently 

 accordant, except in the case of the shorter arcs, the value 475 miles 

 derived for the lowest measurable vapours in 1898 being represented 

 in 1900 by two strata, one reaching to 700 miles and the other to 270 

 miles above the photosphere. 



The bright-line spectrum of the corona was decidedly less bright 

 than in 1898, and a much smaller number of rings is seen in the 

 photographs. The three brightest rings are at wave-lengths 5303*7, 

 4231*3, and 3987*0, and it may be noted that these were also the 

 brightest in the eclipses of 1893, 1896, and 1898. The conclusion 

 that the different rings do not originate in the same gas, arrived at 

 from a discussion of the photographs of 1898, has been confirmed. 



A drawing is given to illustrate the fact that while the details of the 

 green coronal ring are seen in the inner corona, they have no apparent 

 relation to the positions of the great streamers or prominences. For 

 an investigation of this nature the photographs taken with the pris- 

 matic camera of 20 feet focal length are specially valuable. 



" Preliminary Statement on the Prothalli of Ophioglossum pen- 

 dulum (L.) ? Helminthostachys zeylanica (Hook), and Psilohcm, 

 sp." By William H. Lang, M.B., D.Sc., Lecturer in Botany, 

 Queen Margaret College, University of Glasgow. Communi- 

 cated by Professor P. O. Bower, Sc.D., F.K.S. Eeceived 

 May 20— Bead May 23, 1901. 



During a recent visit to Ceylon and the Malay Peninsula* the 

 author found prothalli of Ophioglossum pendulum and Helminthostachys 

 zeylanica, as well as a single specimen, which there is reason to regard 

 as the prothallus of Psilotum. As the examination of the material will 

 occupy a considerable time, it has seemed advisable to give a brief 

 description of the mode of occurrence and external morphology of the 

 prothallus in these three plants, without entering into details of struc- 

 ture or discussing the phylogenetic bearing of the facts. 



The chief gaps in our present knowledge of the gametophytes of the 

 more isolated living Ptericlophyta concern the Ophioglossacece and Lyco- 

 podiacece, to which groups the prothalli described below belong. The 



* The expenses of the visit to the Malay Peninsula were defrayed by a grant 

 from the Royal Society. 



