OBSERVATIONS UPON THE PHENOMENA OF PLANT-LIFE. 305 



for the arraugement of its leaves. Onr squash produced one leaf at each node, 

 aud all the leaves were arranged in two rows on opposite sides of the stem. 

 The vital force in the tip of the vine was very active aud vigorous, and dis- 

 played its power in the constant organization of new nodes. Thus, when we 

 examined the terminal inch of the vine, we found no less than twenty-five 

 young leaves, and in the axils of these twenty-five flowers, including five young 

 squashes, twenty-five branching tendrils, and twenty-five buds for lateral 

 branches. These were continually reproduced, so that when the vine was 

 growing nine inches a day, as well as after it had developed one hundred nodes, 

 the number, was always about the same. All parts of the vine and its append- 

 ages increased with marked unitbrmity. Back of the first inch, which may 

 be regarded as the terminal bud, about six nodes were developing at the same 

 time. The grov/ih was most rapid in the terminal portion of each node, and 

 the leaves were not modified particularly in form during the period of develop- 

 ment. The lengthening of the vine proceeded somewhat irregularly, varying 

 from nothing to nine-sixteenths of an ivch per hour. It Avas usually less 

 between midnight and sunrise than at other iiour?. 



THE LO>hGEST growth 



of the main vine in twenty-four hours was observed August 15 and IG, 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 hundred. At each node of the 

 fully developed vine were found a large leaf; a long, branching tendril, resem- 

 bling 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 dis- 

 tances through which the crude and elaborated saps must 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, containing chlorophyl. 



THE SPECIAL FUXCTIONS OF THE LEAF 



are to absorb carbonic acid from the atmosphere, and, by a process of diges- 

 tion, form from its carbon and the elements of water the soluble starch and 

 sugar, out of which the tissues of the plant are constructed ; to exhale the sur- 

 plus water of the crude sap, and thus aid in its ascension from the soil and the 

 roots; to exhale the oxygen set free in the process of digestion, and thus to 

 purify the air for the respiration of animals ; and finally to exhale, at night 

 eepecially, the surplus carbonic acid liberated within the plant in the process 

 of vegetable respiration, which appears to be as necessary and constant as that 

 of animals. It seems, also, most probable that the albuminoids, or protoplas- 

 22 



