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LIBRARY OF CONGRESS

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LICHENS

mation upon topics of immediate contemporary interests.

The standard books of general reference include such encyclopedias as the Britannica, Americana, Century Cyclopedia of Names, the New International, The Dictionary of National Biography (British) and encyclopaedias and dictionaries of American biography. For the data connected with the lives of prominent living personages, Who's Who and Who's Who in America are handy gazete^s. Many statistics of public interest and often a summary of the chief historical events of the preceding year are to be found in annual almanacs, such as are published by several of New York's leading newspapers.

Among the best dictionaries are: (English) the Oxford and New English dictionaries, Century, Webster, Standard and Worcester', (French) Larousse, Littre and Bes-cherelles; (German) FliegeVs and Grieb's', (Spanish) Velasquez; (Latin) Lewis and Short, Harper, Andrews and Riddle and Arnold; (Greek) Liddell and Scott and Robinson. In addition, dictionaries may be found for every individual subject: music, philosophy, history, art, science and so on. A little determined practice in the use of such books should give the student a habit of verification, which should tend to make his information ^facile and exact.

Library of Congress, The, at Washington, D. C., is the American national library, housed in the finest library building in the world and ranking among the world's best libraries. This is the more remarkable, because in 1814 it was destroyed in the burning of the capitol by the British, and was again partially destroyed in 1851 by fire. The present building was completed in 1897 at a cost of $6,347,000, and will accommodate 2,200,000 octavo volumes. It is freely open for reading and reference purposes; but the books are not lent for home-reading to the general public. The catalogue cards, reference lists and annual reports of the Congressional Library are of great value to all libraries of the United States. The librarian will assist research workers by lists of books upon the topic of his reading; but requests for such aid should be sent through the librarian of the institution through which most of his work is done. The library catalogues all American copyright publications. It has a staff of no less than 400 employees, exclusive of caretakers etc. Some of its chief publications, in addition to the reports of the librarian, are A Union List of Periodicals; A Check List of American Newspapers in the Library of Congress; A List of Maps of America; A Calendar of Washington Manuscripts; and a very large number of topical lists on such subjects as the theory of colonization, mercantile marine subsidies,

the Danish West Indies, Porto Rico, the Monroe Doctrine or the Philippines.

Lichens (U'kens). Plants which are abundant  everywhere,   forming  various-colored

TWO  FORMS   OF   LICHENS

splotches on tree trunks, rocks, old boards etc. and growing also upon the ground. They are of great scientific interest from the fact that they are not single plants, but each lichen is formed of a fungus and an alga living together so intimately as to appear like a single plant. The lichens furnish one of the best illustrations of symbiosis (which see). The fungus makes the bulk of the body with its interwoven mycelial threads, and in the meshes of these threads live the algae. Upon the surface of the lichen body the fungus at certain times develops cup-like or disk-like bodies with brown or black or more brightly colored lining. These bodies are the apothecia (which see) in which the asexual spores are produced. Lichens have a peculiar and effective method of vegetative propagation. Upon the surface of the body there are commonly, seen minute granules which sometimes give the body a dusty appearance. These granules are called soredia, and each consists of a few cells of the alga surrounded by threads of the fungus. These soredia are blown off, and are really small colonies to start new lichen bodies. The lichen fungus is for the most part ian ascomycete (which see), and the accompanying alga is mostly one of the blue-green forms. (See CYANOPHYCE^.) By many it is thought that the fungus and the alga are mutually helpful in this intimate relationship, and if so it would be that form