TRANSACTIONS OF SECTION K. 873 



absence of internal structure, and without a knowledge of details, it is better to 

 adopt the term Equisetites than to include the fossils in the genus Equisetum. 



In tracing the geological history of the Equisetacero it is extremely difficult to 

 determine how far the evidence warrants the reference of certain Palaeozoic fossils 

 til Equisetites rather than to the genus Catamites. The fused leaf-segments usually 

 regarded as characteristic of Equisetites may not be a trustworthy distinguishing 

 i'l'ature. Equisetites Hemitigivayi, Kidst, from the English Coal Measures, and other 

 I'errao-Carboniferous species, afford examples of the difficulties of correct determina- 

 tion. There are certain species of Equisetites of Mesozoic age which present 

 characters of special interest, e.g., Equisetites Beatjii, E. Interalis, and others. An 

 examination of several specimens of these forms has led to the conclusion that the 

 specimens originally described as Calamites Beanii, and afterwards referred to the- 

 Monocotyledons, must be included in the genus Equisetites. Equisetites Beanii, 

 from the Lower Oolite roclis of England, rivalled in size the gigantic Triassic 

 stems described by Schimper and others from the Vosges Sandstones. Equisetites 

 lateralis, regarded by some writers as a form of Phyllotheca or Schizoneura, is, in 

 all probability, a true Equisetites, the reference to the former genera being founded 

 on .in incorrect interpretation of certain specimens. The so-called branch scars 

 of E. lateralis are probably slightly displaced nodal diaphragms. In conclusion 

 the author refers to specimens described as Phyllotheca from various localities and 

 geological horizons, and expresses the opinion that in such cases the generic name 

 Equisetites would be the more appropriate designation. 



On Streptothrix actinomycoticca and allied species q/ Streptotlirix. 

 By Professor E. M. Crookshank, M.D. 



5. Observations on the Cyanophycece. 

 By Professor A. B. Macallum, Fh.D. 



G. Report upon some Preliminary Experiments with the Rontgen Rays on 

 Plants. By George F. Atkinson. 



The experiments were conducted for the purpose of testing the effect of the 

 Rijntgen rays on plants exposed during a considerable period of time. 



Because of the numerous instances of reported injury to the human body as a 

 result of exposure to the Kontgen rays, it has been suggested that it might also 

 have an injurious influence on plants. 



After a few preliminary experiments with leaves of Caladium, flowers of Begonia 

 and seedlings of corn, wheat, sunflower, radish, german-millet, soja-bean, with 

 exposures of one to ten liours, in which no perceptible injury resulted, a longer 

 exposure was made, in which the following seedlings were acted on for a total of 

 forty-five hours in a dark room : sunflower, wheat, german-millet, nonpareil-beau, 

 soja-bean, cotton, oats, corn, vetch, pea, and cucumber. A duplicate set was placed 

 also in the dark room, but outside the range of the Rontgen rays, as a check upon 

 the experiment. 



On some days a continuous run of fifteen hours was made. During this time 

 the plants behaved exactly as plants grown in a dark room would. Some of the 

 seedlings were at one time or another turned strongly towards the light, and at 

 other times just as strongly away from it, and these movements were ascribed to 

 nutation. At the close of the experiment all the growth which had taken place 

 in the dark room was etiolated. On removing the seedlings from the dark room 

 they all became slowly green, but the seedlings which were under the influence of 

 the Rontgen rays recovered the green colour more slowly, which suggests that this- 

 light may h.ave some slight injurious effect on the chloroplastids. No other influ- 

 ence of any land was noted. 



