426 APPENDIX. 



detected by certain of the cells being rounded and broader than 

 others, and some of them at least usually containing the spores, 

 a single spore nearly or quite filling the large cell, or oogonium. 

 When it cannot be studied fresh it may be preserved in 2^ 

 formalin or in 70^ alcohol, first placing it successively in 25^ 

 and 50^ alcohol for a few hours. 



Some species of vaucheria occur in places frequented by 

 oedogonium or spirogyra, while others occur in running water, 

 or still others on damp ground. Frequently fine specimens of 

 vaucheria in fruit may be found during the winter growing on 

 the soil of pots in greenhouses. The jack-in-the-pulpit, also 

 known as Indian turnip, growing in damp ground I have found 

 when potted and grown in the conservatory yields an abundance 

 of the vaucheria, probably the spores of the alga having been 

 transferred with the soil on the plants, ^^'hen material cannot 

 be obtained fresh for study, it may be preserved in advance in 

 formalin or alcohol as described for cedogonium. 



Coleochsete scutata is not so common as the oedogonium, 

 spirogyra, or vaucheria. But it may be sometimes found with 

 the small circular green disks adhering to rushes, grasses, or 

 other aquatic plants in large ponds or on the margins of lakes. 

 When found it is well to make permanent mounts of material 

 killed in formalin, either in glycerine or glycerine jelly. 



Wheat rust. — The cluster-cup stage may be collected in May 

 or June on the leaves of the barberry. Some of the affected 

 leaves may be dried between drying-papers. Other specimens 

 should be preserved in 2;^ formalin or in loi, alcohol. If the 

 cluster cup cannot be found on the barberry, other species may 

 be preserved for study. 



The uredospore and teleutospore stages can usually be found 

 abundantly on wheat and oats, especially on late-sown oats which 

 ripen in autumn. The affected leaves and stems may be pre- 

 served dry. 



The powdery mildews are common during summer and au- 

 tumn on a variety of lca\es of shrul.)s, herbs, and trees. They 

 can be recognized 1)y the mildewed spots, or by the numerous 



