CARYOPHYLLUS. CLOVES. 227 



long and from 40 to 50 microns in diameter. The degree 

 of lignification varies widely. 



The pollen grains are characteristic. They are tetrahe- 

 dral, and may be empty or may contain brownish, oil- 

 stained, protoplasmic contents. They measure about 15 

 microns to a side. 



The vessels are ver}^ delicate, and rarely measure more 

 than 4 to 10 to 15 microns in diameter. They have spiral 

 or annular markings, and may be accompanied by 

 delicate tracheids, measuring about the same in diameter. 



Epidermis cells with stomata do not call for special 

 mention, as these latter are not of any diagnostic signifi- 

 cance. The cr>^stals are small and may readily be over- 

 looked. They measure from 8 to 16 microns. Tissues 

 derived from the petals may be readily recognized by 

 the regular irregularity so characteristic of this type of 

 tissue. In the seed, pitted parenchymatic cells measur- 

 ing 50 to 70 microns are found. These contain irregular 

 shaped starch grains. These are usually simple grains, 

 but are often much compressed and elongated. Some of 

 the larger grains measure from 30 to 35 microns, while 

 the smaller ones average 5 to 7 microns. 



If the powder contains much tissue from the stem the 

 numerous isodiametric sclereids (100 to 130 microns) are 

 foimd, though similar sclereids are also present to some 

 extent in the walls of the fruit. Larger pitted vessels also 

 are indicative of admixture with stem, and the irregular 

 bast fibres are characteristic. Many of these have knob- 

 like ends, and frequently average, according to the 

 measurements of Tschirch and Oesterle, 8 to 26 microns 

 in diameter. In addition to the rosette crystals, cubical 

 crystals 7X7 microns may be found. 



A further chemical reaction is noteworthy in addition 

 to those already described. Solutions of chloride of 

 iron stain most of the tissues dark-blue to black, due, it is 

 said, to the saturation of such tissues with eugenol. 



