part 2] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxxxi 



Loosely arranged and usually un septate tubes, following a slightly 

 tortuous vertical course, associated with smaller and branched 

 tubular elements, make up the tissues of the stem : no certain 

 information is available'as to the nature of the reproductive organs. 

 Silurian and Devonian species agree in essentials. Nematopltycus 

 is generally regarded as an alga ; anatomically it bears a close 

 resemblance to recent members of the Siphonese, while in some 

 respects it recalls the larger brown seaweeds. The association with 

 the problematical genus Pachytheca both in Canada and in Europe, 

 in Silurian as in Devonian rocks, may be significant. With the 

 confidence which his treatment of controversial subjects usually 

 exhibits, Dr. A. H. Church declines to accept Nematophycus as 

 an alga, and assigns it to the Fungi. The point that he makes is in- 

 teresting: a plant such as an alga, which by the aid of chlorophyll 

 and sunlight manufactures its own food, is provided with a super- 

 ficial tissue of short cells, or of cells elongated at right-angles to the 

 source of light. No such tissue had been found in Nematophycus 

 when Dr. Church published his view. In 1921 Dr. R. Kidston 

 and Prof. W. H. Lang, in the fourth of their epoch-making 

 memoirs on the Devonian plants of Ehynie, described a new species, 

 Nematophycus taiti, founded on a very small petrified fragment : 

 a second fragment was described, which, in addition to some vertical 

 tubes, showed a patch of peripheral tissue consisting of tubular 

 elements elongated at right-angles to the surface, a feature de- 

 manded by Dr. Church if the genus is to be included in the algas. 

 Through the kindness of my friend Dr. Kidston, I was able to ex- 

 amine the Rhynie material ; and, while it would be presumptuous 

 on my part, after a short inspection of the sections, to question the 

 accuracy of the identification given by the authors of the new 

 species, I cannot refrain from wondering whether the fragments 

 do not agree more closely with the type of structure represented by 

 the genus Pachytheca, a genus which indeed may be incorrectly 

 separated from Nematophycus. Until additional and larger speci- 

 mens are discovered, it is hardly possible, either whole-heartedly 

 to accept the conclusions of Kidston & Lang, or definitely to doubt 

 their accuracy. If the Rhyme plant is Nematophycus, its discovery 

 supports the old view of Dawson that it grew on land : it occurs 

 in association with the flora of a Devonian marsh. After discussing 

 this point, Kidston & Lang conclude that 'whatever its systematic 

 affinities may prove to be', Nematopliycus may have been 'a marsh- 

 or land-plant of Silurian and Devonian times '. One is tempted to 



TOL. LXXIX. f 



