2330 Journal of Applied Microscopy 



may be fairly questioned if other means of division than small halls or rooms 

 should not be chosen as screens, temporary alcove walls, and accentuated mount- 

 ings around the object, than to checker-board a great museum with cells, pock- 

 ets, lanes and boxes. 



Dimensions in composite halls may assume many degrees, but it is well, 

 under ordinary circumstances to make the sides of a polygonal hall 7iot less than 

 15 feet, which allows for windows ; the diameter of circular halls not less than 30 

 feet if terminal, or not less than 45 feet if central, and the longer axis of elliptical 

 halls not less than 100 feet. Such directions are suggestive and afford a table 

 of reference from which variations may be reasonably made. 

 American Museum of Natural History. L-- "• GrataCAP. 



Laboratory Outlines for the Elementary Study of Plant 



Structures and Functions from the Standpoint 



of Evolution. 



THE HIGHER FUNGI AND LICHENS— Continued. 



XXXVI. Puccinia graminis Pers. Wheat Rust. 



Class, Hemibasidii. Order, Uredinales. Family, Pucciniaceae. 



The aecidium stage of the wheat rust occurs in the spring on the leaves of 

 Berberis vulgaris : the uredo stage, known as red rust, and the teleuto stage, 

 known as black rust, occur on the wheat plant. The infected leaves of the bar- 

 berry may be preserved in 70 per cent, alcohol and the wheat leaves and stems 

 may be dried or also preserved in alcohol. 



Aecidium stage. 



1. Study the under side of a barberry leaf containing the rust under dis- 

 secting microscope. Sketch an entire leaf, representing the position of the dis- 

 eased spots. 



2. Under low power draw a spot showing the aecidia — cup-like bodies con- 

 taining the aecidiospores. 



3. Under low power examine a spot on the upper side of the leaf and note 

 the little crater-like openings, which are the necks of sac-like bodies, called 

 " spermogonia " (pycnidia), containing thread-like conidia. Draw. 



4. By means of elder pith or strips of carrot and a razor cut cross sections 

 of the leaf, mount, and study under low power. Under high power draw an 

 aecidium, showing the aecidiospores. How are they developed. Draw a spermo- 

 gonium with conidia. 



Uredo stage. 



5. Under low power, study the diseased spots on the leaves and stems of 

 wheat {Triticurn vulgare). Draw a patch, showing how the spores break through 

 the epidermis. 



6. Pick out some uredospores with a needle, or if fresh material is at hand 

 cut cross sections of the stem, mount, and draw the uredospores under high 

 power. 



