174 



SCIENCE. 



[N. S. Vol. XIX. Xo.474. 



only with low osmotic pressure and they 

 germinate to form filaments. If filaments 

 are placed in a medium of high pressure 

 they break up into round cells or form 

 groups of round cells. "When the solution 

 of low osmotic pressure has added to it a 

 trace of such a poison as nitric or sulfuric 

 acid, copper sulphate, silver nitrate, etc., 

 the alga takes the Palmella form as though 

 the pressure were high. If the poison is 

 still more dilute there is a stimulation of 

 zoospore production, though the zoospores 

 are checked in germination. Nitrates and 

 sulphates were used and it appears that 

 the poison kations have the effect of pro- 

 ducing the Palmella form in a solution 

 whose osmotic pressure is far too low to 

 bring about this result. The kations so far 

 studied are: H, Li, Rb, NH„ Cu, Ag, Al 

 and Fe. All of these also produce stimula- 

 tion of zoospore production when in 

 weaker solution, and to the list may be* 

 added Ba and Sr. 



The Differentiation of the Strohilus: F. E. 



Clements. 



(1) A brief consideration of the anti- 

 thetic evolution of the sporophyte from 

 Tetraspora to Anthoceros; (2) a discus- 

 sion of the probable origin of Selaginella 

 and Isoetes; (3) the derivation of the stro- 

 bilus of Pinus, Myosurus and Alisma from 

 Selaginella; (4) the general ecological 

 principles involved in the modification of 

 the strobilus; (5) the essentials of the 

 phylogenetic method. 



The Histology of Insect Galls : M. T. Cook. 

 The function of the gall is to furnish 

 nutrition and protection for the larva. 

 The simplest galls only show two zones, 

 the inner nutritive and the outer pro- 

 tective. The most highly developed galls 

 show four zones, the second and third 

 often separated; the innermost zone is nu- 

 tritive and the other protective. "When 

 the gall first forms it is a mass of irregular 



parenchyma cells which soon become dif- 

 ferentiated into the zones. In the simplest 

 galls, where we have only two zones, the 

 inner nutritive zone is rich in protoplasm, 

 starch, etc., until the insect is near ma- 

 turity, while the other zone forms tannin. 

 In the most highly developed galls, tannin 

 is also developed in abundance. The in- 

 nermost zone is very rich in nutrition, the 

 remaining three zones are protective. The 

 separation of the second and third zone is 

 undoubtedly a protective device. The 

 shape of the gall and its complexity are 

 probably due to efforts for protection 

 against parasites and birds. 



Morphology of Caryophyllacece: M. T. 



Cook. 



Some time since the Avriter published a 

 short paper on Agrostemma Githago L. and 

 Claytonia Virginica L. Among the most 

 interesting points in these papers was the 

 formation of the pecidiar beak to the ovule 

 and the two zones of the nucellus in A. 

 Githago. The writer has since continued 

 the study upon two species of the Caryo- 

 phyllacese for the purpose of demonstrat- 

 ing the importance, if any, of the morphol- 

 ogy of the embryo sac and surrounding 

 structure in taxonomy. The two species 

 selected for study were Vaccaria Vaccaria 

 (L.) Britton and Alsine puhera (Michx.) 

 Britton. In both cases a beak is formed 

 similar to A. Githago and the embryo fol- 

 lows a similar line of development, but the 

 sac enlarges in the same manner and di- 

 rection as in C. Virginica. Other points 

 are as yet not definitely determined. 



The Phytogeny and Development of the 

 Archegonium. of 3Inium cuspidatum: G. 



M. HOLFERTY. 



After brief statements in regard to the 

 collection and method of treatment of ma- 

 terial, and the terminology to be used, the 

 author reviews the more important litera- 



