242 University of California Publications. [Botany 



prevent the loss of much of the material unless it adheres firmly 

 in a mass. 



After the material is washed, it may be placed directly in a 

 dialyzer,'and by this means slowly dehydrated, thus preventing 

 shrinkage and also the loss of material. 



The embedding and cutting of material is at best a slow pro- 

 cess, requiring skill and patience to secure sections suitable for 

 careful study. Experience has shown that many things may be 

 learned about the cell by the use of other methods which facili- 

 tate the work and enable one to arrive at the same results in a 

 much shorter time. In fact, it is only in exceptional cases that 

 one needs microtome sections. So far I have been able to demon- 

 strate everything which was revealed by the thin sections without 

 resorting to cutting, and consequently use sections now only to 

 supplement and check results obtained without it. Everything 

 may be seen in the small plants, only a few microns thick, if prop- 

 erly stained. 



It is also desirable to study the nucleus as a whole, in longi- 

 tudinal view, and this has been found to be possible and practical 

 in uncut cells. 



Most of the forms have a sufficiently gelatinous wall to cause 

 them to adhere to the slide without any assistance, and may be 

 stained, washed, and permanently mounted within a few minutes, 

 provided a study is to be made without previously killing them. 

 If it is desired to kill them previous to staining, this may be done 

 by placing the slide with the adhering material directly in the 

 killing agent, after which it may be washed, stained, and treated 

 as desired. The more they are handled, the more liable are the 

 specimens to be lost, and if one has forms like Oscillatoria, which 

 are not very gelatinous, it is well to place on the slide first a little 

 albumen fixative. Nostocs, Anabaenas, etc., of the heterocysted 

 group, do not require this, being sufficiently gelatinous to adhere 

 firmly to the slide. 



It is highly desirable to get the material spread out very thin 

 on the slide, and a good method for doing this with the rapidly 

 crawling forms is to allow them to spread out on the surface of 

 the water, as mentioned above, trim off small pieces, which should 

 be carefully floated upon a slide (this may be previously smeared 



