78 MICROSCOPIC OBJECTS. 



The pollen of the Gesneria hulhosa, Datura Stramo- 

 nium, Ipomcea hederacea, and others, when immersed in a 

 few drops of weak acid placed upon a slider under the 

 microscope, emits a tube of some length. The granular 

 matter in the pollen may then be seen to pass along the 

 tube until the pollen is emptied. Mr. Bauer is of 

 opinion that the matter expelled is not tubular, but 

 simply mucus with a few grains attached. This subject 

 is worthy of investigation, as some botanists not only 

 believe in the tube, but state that by it the fecundating 

 particles of the pollen enter the ovary. 



In Orchideous plants the forms of the Pollen-masses 

 are curious and interesting microscopic subjects. The 

 specimens should be preserved on black discs. 



The diameter of the pollen varies very much in different 

 plants : among the smallest are those of the Sensitive 

 Plant fMimosa sensitivaj. 



The magnifying power for vievdng pollen as opaque 

 bodies should be from 30 to 60 diameters. For observing 

 the tube and experimenting on them as transparent 

 objects with dilute acid, a power of 200 to 400 diameters 

 is required. 



Algce. — This the lowest tribe of the vegetable king- 

 dom is considered by Dr. Lindley as closely allied in 

 organization to the Fungi and Lichens. They are dis- 

 tinguished from both those tribes in being aquatic. The 

 number and variety of the species of Algae, together 

 with their minuteness, render them appropriate subjects 

 for microscopical study. The green mucous slirne-Hke 



