THE MICROSCOPE IN HISTOLOGY AND BOTANY. 157 



2. Leaves. These should be examined by thin longitu- 

 dinal and transverse sections. The epidermis of both sides 

 should be detached, and the position and arrangement of 

 the stomata observed (Plate VII, Fig. 100). The hairs 

 of the epidermis, the arrangement of the parenchyma, and 

 the distribution of the vascular bundles in the form of 

 nerves, are also of importance. 



3. Flowers. For ascertaining the number and position 

 of the parts of the flower, transverse sections at different 

 heights through an unopened bud may be taken, together 

 with a longitudinal section exactly through the middle. 

 The general structure of sepals and petals corresponds with 

 that of leaves, but there are some peculiarities. Thus the 

 cells of the petal of the geranium exhibit when deprived 

 of epidermis, dried and mounted in balsam, a peculiar 

 mammillated appearance with radiating hairs (Plate VIII, 

 Fig. 102). Anthers and pollen grains are also interesting 

 microscopic objects. The protrusion of the inner mem- 

 brane through the exterior pores in pollen may be stimu- 

 lated by moistening with water, dilute acid, etc. The 

 penetration of the pollen tubes through the tissue of the 

 style may be traced by sections or careful dissection. The 

 heartsease, viola tricolor, and the black and red currant, 

 ribes nigrum and rubrum, have been recommended for this 

 purpose. 



4. Seeds. The reticulations or markings on various 

 kinds of seeds render them frequent objects for observa- 

 tion with the binocular microscope. Adulterations may 

 also be detected in this way, as well as imperfect seeds in 

 any sample, a subject of much importance to the practical 

 farmer. 



