460 



SCIENCE. 



[N. S. Vol. XVII. No. 429. 



most injurious. The last-mentioned are 

 followed by some salts of potassium and 

 calcium in irregular order, although it is 

 to be noted that potassium nitrate is about 

 twice as poisonous as potassium chloride. 

 The least toxic ax*e the salts of sodium and 

 magnesium. An average of the experi- 

 ments shows magnesium sulphate to be the 

 least toxic of all salts which have been 

 used as sulphates, chlorides or nitrates. 

 The low toxicity of the magnesium salts 

 with relation to the marine algse makes it 

 evident that these plants are very notable 

 exceptions to the rule which Loew and 

 others found to hold for many phanero- 

 gams and fresh-water algas. 



The toxicity of the salts studied bore no 

 close relation to the relative amounts of 

 these salts normally present in sea water. 

 The inconsistent results with potassium 

 nitrate and other salts as plasmolytic 

 agents may be partially explained by the 

 toxic action of these salts on the marine 

 algee. 



The Nature and Function of the Pyrenoid: 

 Mr. H. G. TiMBERLAKE, University of 

 "Wisconsin. 



Among the structures found in the cells 

 of the green algse the pyrenoid occupies a 

 doubtful position. The question as to 

 whether it is to be considered a true cell- 

 organ or a mere mass of reserve material 

 is partly, but not wholly, solved by its his- 

 tory in connection with the various phases 

 of the life history of the cell and its rela- 

 tion to the process of starch formation. 

 That the pyrenoid may be reproduced by 

 division is shown in the cells of Cladophora, 

 GEdogonium and other filamentous algte, 

 as also in Chlamydomonas among the uni- 

 cellular forms. In this latter case the 

 pyrenoid divides during the division of the 

 cell. On the other hand, it is well estab- 

 lished that under ordinary circumstances 

 the pyrenoids entirely disappear prior to 



spore formation in Hydrodictyon and are 

 afterward formed anew in the young cells. 



The relation of the pyrenoid to starch 

 formation in Cladophora and other forms 

 studied is essentially the same as that al- 

 ready described by the author for Hydro- 

 dictyon {Annals of Botany, December, 

 1901). The following additional details 

 are noted : The usual shape of the pyrenoid 

 in the species of Cladophora studied is that 

 of a biconvex lens. The differentiation of 

 the pyrenoid into two parts takes place in 

 such a way as to divide it by a plane pass- 

 ing through its longer axis. In many 

 cases the pyrenoid is actually split into 

 halves with a fairly' broad cleft between 

 them. Either of the halves so formed may 

 be converted into a starch grain. In some 

 instances the entire pyrenoid is converted 

 into starch without previous cleavage. 

 This is more apt to happen in CEdogonium 

 and Bhizoclonium than in Cladophora. 



The nature of the chemical processes in- 

 volved in the formation of starch from a 

 pyrenoid is now under investigation. 

 That the process involves a conversion of 

 a proteid substance (the pyrenoid) into a 

 carbohydrate (starch) seems reasonably 

 certain, but the unreliable character of 

 various microchemical reactions makes the 

 study of the details very difficult. 



Observations upon the Morphology of a 

 Species of Osmunda from the Cretaceous 

 Formation, and its Relation to Existing 

 Species: Professor D. P. Penhallow, 

 McGill University. 



In material from the Cretaceous of 

 Skidegate Inlet, Queen Charlotte Islands, 

 collected by Dr. C. F. Newcombe in 1895 

 and 1897, there were several fragments of 

 plants representing the stipe, rhizome, fer- 

 tile and sterile pinnules of a fern. Al- 

 though not in actual connection, these 

 fragments proved, upon examination, to 

 belong to the same genus and undoubtedly 



