74 VEGETABLE HISTOLOGY. 



prothallia of ferns, Eel-grass, Water-weed, are excellent objects 

 of study. 



Mount a few fresh leaves of a moss in water and examine the 

 cells lying near the edge of the leaf. The cells contain numer- 

 ous rounded greenish bodies the chlorophyll bodies. Note 

 the closely-packed, rectangular-shaped, somewhat thick-walled 

 cells. Try to observe chlorophyll bodies that are constricted 

 in the middle. Such are in the act of division. 



Run strong alcohol under the cover glass. The green bodies 

 are slowly bleached, the chlorophyll is dissolved out and forms a 

 greenish solution in the cells. From this experiment it is con- 

 cluded that the bodies consist of two parts, a proteid ground 

 work, through which is diffused the chlorophyll or green color 

 substance. 



Add iodine solution to a leaf that has been bleached with 

 alcohol. The transparent protoplasm of the cells is now 

 stained brown and made visible. The ground substance of the 

 chloroplasts also stains brown, indicating a proteid substance. 



Starch grains in chloroplasts. Put some leaves of a vigor- 

 ously-growing moss that has been exposed to sunlight for two 

 or three hours in alcohol until bleached. Then mount a leaf 

 in water, focus it and apply a drop of chloral-hydrate iodine 

 solution at the edge of the cover glass and watch closely the 

 chlorophyll body as the reagent comes in contact with it. The 

 ground substance is seen to swell rapidly and becomes trans- 

 parent, leaving the starch grains stained blue, visible. The 

 latter are small and elongated. By the continued action of the 

 chloral the whole structure gradually disappears. The starch 

 that is formed in the chlorophyll bodies in the daytime is dis- 

 solved during the night and transferred to other parts of the 

 plant. 



CHAPTER XVIII. 



SECRETION SACS, INTERCELLULAR AIR SPACES AND SECRETION 



RESERVOIRS. 



Some cells at maturity lose their protoplasm and their proper 

 cell character and become filled with secreted matters. These 

 form the secretion sacs. They are of various forms, but more 

 commonly resemble parenchyma cells in appearance and char- 

 acter of their walls. Sometimes they are much elongated and 

 resemble latex tissue. The sacs are given names according to 

 the secretion they contain, thus, resin sacs, mucilage sacs, etc. 



Intercellular air spaces are more or less abundant in nearly 

 all multicellular plants, their probable function being to supply 

 air to the interior tissues for respiratory purposes. In aquatics 

 the spaces are usually large and often regular in shape, while 



