Comjjarative Studi/ of Chloroplujll. 395 



of a finely granular mass of green protoplasm, arranged in 

 the form of a network, or it is perhaps more correct to say, 

 rendered spongy by the presence of a fatty material, the 

 greater part of which usually aggregates to form oil-globules 

 of various sizes, while a small quantity is diffused through 

 the ground-substance. The larger oil-globules may be 

 recognised by looking for granules which will, according to 

 focussing, either become darker or lighter than the ground- 

 substance ; and sometimes it is possible to make out that 

 these globules are slightly yellowish-green compared with the 

 green protoplasm. 



In vigorous threads I have several times seen a vibrating 

 motion in the green ground-substance, specially near the 

 oil-globules, and also by looking along the clear protoplasmic 

 envelope of the chloroplast that small bulgings are formed, 

 which after a time will collapse ; and I believe that when 

 the bulgings collapse a small quantity of oily material is 

 given out directly into the surrounding protoplasm, and that 

 the material may be seen there as minute granules, smaller 

 than the microsomata. I have, however, not been able to 

 make out the actual cutting off of the granules, although I 

 looked most carefully. 



These observations on perfectly normal material seem to 

 be verified by the use of staining reagents, and the stains I 

 found to answer my purpose best are — 



1. Cyanin, or Bleu dc Quinolein, in a 10 per cent. 



solution in absolute alcohol. 



2. Tincture of Alcanna root, concentrated till a preci- 



pitate begins to form. 



3. Osmic acid in a 1 per cent, solution. 



Cyanin has a remarkable affinity for all fatty bodies, 

 staining them a bright blue colour, and as it is readily 

 taken up by Spirogyra without seemingly doing much harm, 

 if sufficiently diluted, it is of the highest value in ascertaining 

 where exactly fatty material occurs in a cell. To stain the 

 chlorophyll-bands most successfully, I found the following 

 plan the best : — A glass vessel is tilled with two litres of 

 water, to which six drops of the above-stated solution of 

 Cyanin are added ; then a small quantity of either Spiro- 

 gyra jugalis or Spirogyra nitida is placed in the vessel, and 



