138 C. M. CHILD. 



plasmic disintegration observed with other agents can be clearly 

 seen. 



In a study of the determination of polarity by light in the egg 

 of the alga Fuciis vesiculosus, permanganate and various other 

 agents were used. As is well known, the first steps in Fucus 

 development are the cell division with the membrane at right 

 angles to the direction of incident light and the outgrowth of 

 the rhizoid on the side of the egg away from the light. The 

 color gradient with permanganate as well as the susceptibility 

 gradients with KNC and various other agents showed that in 

 the early stages the rhizoid outgrowth stains first and is most 

 susceptible, but that after three to five days a region of rapid 

 staining and high susceptibility begins to arise at the opposite 

 end of the developing plant and this second region becomes and 

 remains the region of highest rate of oxidation as indicated by 

 these methods and forms the apical growing region of the thallus. 

 These data are merely recorded here and will be considered more 

 fully at another time. 



Perhaps the most interesting observations among those made 

 on plants concern a diatom of the Navicula group. In this form 

 the individuals, bound together by a transparent jelly-like secre- 

 tion, form an alga-like structure, a pseudothallus, often reaching 

 a length of several centimeters, which shows a definitely directed 

 growth, regular and orderly bifurcation, and in short possesses 

 all the external morphological characteristics of a multiaxiate, 

 branching alga thallus. The appearance of this pseudothallus 

 suggests very clearly that growth and multiplication of the 

 diatoms composing it occur chiefly in the terminal regions of the 

 branches, in fact, it is difficult to account for the orderly axiate 

 habitus on any other basis. In the light of these facts, it is 

 interesting to record that this pseudothallus composed of diatoms 

 shows in permanganate a definite basipetal staining gradient in 

 each branch or axis, for at least several millimeters from the tip, 

 although further basally irregularities appear. A similar gradient 

 in susceptibility has also been observed. In this form then 

 although protoplasm'c continuity from, diatom to diatom sup- 

 posedly does not exist, there is a definite, orderly relation, a 

 gradient in physiological condition along each axis, as in axiate 



