4.8 THE PLANT WORLD. 



Everyone is familiar with the Cinnamon vine {Dioscorea Batatas), 

 its clean, glossy foliage and rapid growth rendering it a universal 

 favorite. The so-called Air Potato, however, a tropical species of the 

 same genus, is apparently not well-known outside of Florida, where 

 it is often grown for the sake of the large, edible tubers that form in 

 the axils of the leaves. During the past summer this vine has covered 

 a post in my garden with its luxuriant green foliage. The leaves are 

 almost orbicular in outline, and fully three times as large as those of 

 the cinnamon vine ; and there are now several tubers hanging from 

 the main stem. — C. L. Pollard 



According to Professor Joseph LeConte of the University of Cal- 

 ifornia, a vigorous vegetation, as for example an average field-crop or 

 a thick forest, makes about 2,000 pounds of dried organic matter per 

 annum per acre, or 100 tons per century. But 100 tons of vegetable 

 matter compressed to the specific gravity of coal and spread over 

 an acre would make a layer less than two-thirds of an inch deep. Yet 

 vegetable matter in changing to coal loses on an average four-fifths of 

 its weight, and therefore vigorous vegetation at present could make 

 only about one-eighth of an inch of coal per century. To make a layer 

 one foot thick would require nearly ten thousand years, but the aggre- 

 gate thickness in certain coal basins is 100 or even 150 feet, and this 

 would require, the former nearly a million and the latter a million 

 four hundred thousand years. 



In September last, while operating in southwestern Kansas, near 

 Belvidere, Kiowa county, Mr. C. N. Gould of Southwest Kansas Col- 

 lege, Winfield, Kansas, who was in my party, informed me that some 

 nine miles southeast of Belvidere, on Elk Creek, near the northeast 

 corner of Comanche county, he had seen a little thorny bush bearing 

 bean-pods, that no one could name for him. I at once suspected it to 

 be the mesquite, but had never heard of its growing north of Texas, 

 the boundary line of which is some 300 miles south of that point. On 

 the 15th we visited this place, and Mr. Gould pointed out the bush. 

 It was only four feet high, and fruiting profusely. My suspicions 

 were fully sustained, as it proved to be the Prosopis Jiiliflora, at least 

 that form of it in which the leaflets are set far apart, and which was 

 called P. glandulosa by Torrey, w^ho considered it distinct from the 

 form in Arizona and westward. This is almost certainly the most north- 

 ern point at which this genus has thus far been found, and it does not 

 occur in any of the books that include only the State of Kansas in their 

 southern range. Its low, stunted character further shows that this lit- 

 tle straggler was out of its normal habitat and had reached its 

 extreme northern limit. The spot is about twenty-five miles north of 

 the Kansas-Oklahoma line. — Lester F. Ward, U. S. National Museum. 



