FUNCTIONS OF THE LEAF. 213 



five buds for lateral branches. These were continually repro- 

 duced, so that when the vine was growing nine inches a day, 

 as well as after it had developed one hundred nodes, the num- 

 ber was always about the same. All parts of the vine and 

 its appendages increased with marked uniformity. Back of 

 the first inch, which may be regarded as the terminal bud, 

 about six nodes were developing at the same time. The 

 growth was most rapid in the terminal portion of each node, 

 and the leaves were not modified particularly in form during 

 the period of development. The lengthening of the vine pro- 

 ceeded somewhat irregularly, varying from nothing to nine- 

 sixteenths of an inch per hour. It was usually less between 

 midnight and sunrise than at other hours. 



The longest growth of the main vine in twenty-four hours 

 was observed August 15th and 16th, from 7 a. m. to 7 a. m., 

 and amounted to nine inches. The laterals were removed when 

 two or three feet in length. The total extent of the main 

 vine was fifty-two feet, and the number of nodes was one hun- 

 dred. At each node of the fully-developed vine were found a 

 large leaf; a long, branching tendril, resembling the veins of a 

 leaf, without the intervening cellular tissue ; a staminate flower 

 on a long stalk, or a pistillate flower on a short stalk ; a 

 lateral branch, and, on the under side of the vine, a long, 

 branching root. The function of this root was evidently to 

 supply water to the leaf above it, and its development, of 

 course, depended chiefly upon the nutrient material elaborated 

 by this leaf. These nodal roots not only furnished a much 

 larger feeding-ground for the plant, but saved an immense 

 amount of mechanical work in reducing the distances through 

 which the crude and elaborated saps ihust be carried. 



The largest leaves of the squash-vine were nearly circular, 

 and slightly lobed, with a diameter of two feet and a half, 

 and a superficial area of about seven hundred square inches. 

 The leaf-stalks were hollow, two feet in length, and curiously 

 marked with vertical striae, alternately light and dark in color. 

 The light lines were found to contain bundles of fibro-vascular 

 tissue, while the dark ones were simple cellular tissue, con- 

 taining chlorophyl. 



The special functions of the leaf are to absorb carbonic acid 

 from the atmosphere, and, by a process of digestion, form 



