78 THE AMERICAN BOTANIST 



terested in promoting travel in this way, and it has issued a 

 Hst of about 450 desirable camping places in various parts of 

 England. There seems to be no reason, however, why cara- 

 vanning should remain a source of enjoyment for Europeans 

 only. Our own country contains as many beautiful scenes, 

 but they are much too often seen through a dusty haze raised 

 by the automobile. A roomy wagon — essentially a summer 

 house on wheels — offers numerous advantages over the 

 automobile which has, in fact little except speed to recom- 

 mend it, but the gypsies are apparently the only ones on this 

 side to be aware of it. Occasionally a company of botanists 

 may make a trip by wagon into an unfrequented region, but a 

 vacation trip by van is still a rarity with us, though it offers 

 one of the best means of studying our plants as they grow. 



Coral Reefs Made by Plants. — Whether we have 

 visited the tropics or not, we are, at least, familiar with the 

 idea of coral reefs. It used to be stated that a coral reef is a 

 ridge or mound of limestone built up by the "coral insect." 

 Long ago, however, it was discovered that the animal which 

 forms coral is not an insect, but it is only recently that still 

 more important discoveries have shown us that many, prob- 

 ably a majority, of the ridges reputed to be coral reefs are not 

 made by the coral polyp. Of course all true coral reefs have 

 been made by the coral animal but it now appears that coral 

 reefs are not as abundant as once believed, and that the ma- 

 jority of reefs have been built up by plants instead of animals. 

 Among the Algae, which include the seaweeds, there are a con- 

 siderable number of species that have the faculty of secreting 

 lime or at least calcium carbonate. The common species of 

 Chara are examples of fresh-water forms with this habit and 

 in the ocean are many others notably Lithothamnion, Gon- 

 iolithon, Lithophyllum,^ Halimeda, Phymatolithion and other 

 species forming the group known as the coralline seaweeds. 

 These rapidly accumulate carbonate of lime and thus build up 



