BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [22] 



but when tliey are attached to rocks it will be found next to impossible 

 to remove them, and as thin a stratum of the rock as can be obtained 

 without injury to the plants must be taken with them, These rock- 

 growing lichens are generally very brittle, and care must be taken not 

 to crush them. On this account lichens can best be collected during or 

 just after a rain storm, as they are then less liable to injury, being freely 

 hygroscopic. 



" In collecting lichens I find it a great convenience to have along with 

 me some small paper bags, such as grocers use. They take up very 

 little room until wanted, and lichens put into them may be pre 

 vented from rattling around and breaking to pieces, as many of them 

 will do if thrown into a box." (F. Le Koy Sargent in Botanical Gazette, 

 XI, p. 142.) 



The crustaceous forms will require no care in drying, but the larger 

 foliaceous ones may be dried under a very light pressure. All should 

 be collected, as near as can be determined, in fruit. 



FRESH-WATER ALGiE. 



Fresh water algte occur in a great variety of situations, such as 

 ponds, quiet or sluggish waters, cascades, ravines, shaded and dripping- 

 rocks, shallow, quiet angles of lakes, and even rapid running brooks 

 or rivers. The implements required for collecting them are simply 

 some appliance for securing them from the water, such as a dredge or 

 dip-net, and a number of wide-mouthed vials. The larger filamentous 

 forms may be well preserved in pieces of brown j)aper a few inches 

 square. The bottled -material may be preserved in good condition for 

 many mouths by the addition of a few drops of carbolic acid. 



" It may be well to bear in mind that the freshest and brightest green 

 forms are not usually the most desirable. Among the older and more 

 unsightly material more mature and fruiting specimens maybe found."— 

 (Francis Wolle in Botanical Gazette, xi, p. 148.) 



Desmids are most frequently found in abundance in clear, pure 

 water, as pools fed by springs, ponds of clear water, etc. They are 

 found attached to the stems of aquatic plants and other submerged 

 objects. They may be obtained by dipping or by strij^ping the stems 

 and leaves of water plants. Sphagnum moss which is growing under 

 water is a very fruitful source for them. They may be preserved in 

 vials or mounted as microscopic slides in cells of glycerine, water with 

 a small amount of preservative fluid, or in the especially prepared 

 mounting media. 



Nostocs may be preserved between sheets of glass or put on pieces 

 of mica and dried in the air. 



Marine alg^.* 

 Marine algse may be collected (1) by hand, as from uncovered rocks 



* From notes cominunicatecl by Prof. Edward S. Burgess. 



