February 13, 1914] 



SCIENCE 



261 



ing not more than four or five genera. By a pure 

 culture here is understood one containing a single 

 species of alga free from all other organisms. 

 What work has been done with pure cultures has 

 led invariably to the conclusion that these forms 

 are unable to fix free atmospheric nitrogen both 

 in the presence of and absence of combined ni- 

 trogen and energy-furnishing materials. It is by 

 no means certain, however, that forms do not ex- 

 ist which under one or all of these conditions are 

 able to utilize elementary nitrogen. This thought 

 is especially justified when the small number of 

 free nitrogen-fixing species among the bacteria 

 are considered. 



By a variety of methods approximately 25 spe- 

 cies were isolated in pure culture. Of these, two 

 were blue-greens, 2 diatoms, and the remainder 

 grass-greens. Seven species of the latter were 

 tested for free nitrogen fixation in the complete 

 absence of combined nitrogen. The effect of a 

 slightly elevated temperature was determined in 

 a duplicate series maintained at a temperature 

 of from 29.5 to 30.5° C. 



No fixation was observed in any of the species 

 and, unlike certain fungi, no favorable effect was 

 exercised by the higher temperature. 

 Indications Bespecting the Source of Comliined 



Nitrogen Used by Viva lactuca: G. L. Foster. 



Laboratory cultures of Ulva lactuca in sea- 

 water showed increased growth over that of the 

 controls, when ammonium nitrate, urea or acetan- 

 ide was added. Na-asparaginate did not increase 

 the growth. Dimethylanilin and acetanilide were 

 extremely toxic. 



Parallel experiments in which the same com- 

 pounds were added to artificial sea-water less 

 nitrogen, gave similar results. 

 The Influence of Etherisation on Certain Ensy- 



matic Activities of Bulbs and Tubers: M. M. 



McCooL. 



The experiments reported deal chiefly with the 

 relative activity of diastases, oxidases and cata- 

 lase in etherized and natural bulbs and tubers. 

 Material from the two sources indicated differ ma- 

 terially in the activity of the enzymes. Diastatic 

 action is greater in the etherized tissues; and this 

 is also true for the action of oxidases and per- 

 oxidases. Catalase activity is, however, dimin- 

 ished by etherization. 

 On the Tracheary Origin of the Resin Tissue of 



the Conifers with Special Meference to Abies 



balsamea: R. B. ThomsoW. 



After a careful survey of the resin tissue in the 



whole CJonifer series, the conclusion has been 

 reached that the ligneous resin tissue of the Coni- 

 fers owes its origin to the modification of tra- 

 cheary elements. This seems self-evident when it 

 is considered that the Cordaitean forms, from which 

 the Conifers are generally conceded to have arisen, 

 have wood which is wholly tracheary. This view 

 is directly opposed to that of Penhallow, who re- 

 gards the resin tissue as derived from parenchyma, 

 a view which is no doubt responsible for the recent 

 theory of Kirsch that the vertical resin canals of 

 the pines are proliferated from the parenchyma of 

 the medullary rays. 



In Abies Penhallow found transitions between 

 the parenchymatous cells of the resin cysts and 

 parenehynia-shaped tracheary elements. These he 

 interpreted as evidence of the transformation of 

 parenchyma into tracheary elements, whereas the 

 writer presents evidence to show that both these 

 and the parenchyma elements are derivatives 

 of tracheids, the chief point being that these ele- 

 ments or combinations of them and the parenchy- 

 matous ones are in vertical series coterminous 

 and in the same radial sequence with ordinary 

 tracheids. They are thus derived from the same 

 cambial cell which ordinarily gives rise to a 

 tracheid. The modification occurs in association 

 with the medullary rays, which are the only source 

 of preservative in the most ancient fossil woods. 

 Cycad Pitting: H. B. SirTON. 



The pits on different parts of individual tra- 

 cheids of the Cycads differ. The terminal ones, 

 and those on the sides touching pa.renchyma tissue 

 are more primitive than the others: In arrange- 

 ment the pits are opposite or alternate indiscrimi- 

 nately, and are even quite commonly scattered or 

 in small groups of two or three, facts which show 

 that the arrangement of pits is not a feature of so 

 great phylogenetic importance as has been thought. 

 In cases of scattered or group pitting, there is 

 present a probable precursor or primitive form of 

 the "bars" or "rims" of Sanio, structures which 

 have not been previously described in the Cycads, 

 the only group of living Gymnosperms in which 

 they have not been found. 



A reexamination of type material of Cordaites 

 missouriense (C. illinoisense) reveal several im- 

 portant features not mentioned in Penhallow 's 

 brief description. 



The pitting is more primitive near the ends of 

 the tracheids, and beside the medullary rays, than 

 on other parts. This is shown by an increase 

 in the number of rows of pits, and by the greater 



