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oles and ramifying in the veins of the leaves. It seems to follow from this that whatever be the path of the water current in the stem itself, it can enter the body of the plant in quantities sufficient for transpiration purposes only along the pathway of the spirals, and can reach the leaves only through the same channels.

The pitted vessels are probably sometimes nearly full of water, and at other times nearly empty, the amount depending on the quantity in the soil and on the activity of transpiration. Owing to the number of very thin places or actual perforations in their walls, they undoubtedly contain air at all times and probably often in large quantities. I regard these vessels as water reservoirs. In this capacity they appear to be admirably adapted to serve the needs of a class of plants which (on account of the extent and unprotected nature of their transpiring surface) often make sudden and very large demands on the stem for water,-demands greater than can be met by the immediate activity of the roots. There is, however, nothing against the supposition that when they are not full of water, they may also serve as aerating organs, the stems being alive and chlorophyll-bearing clear to the center. The function of the spiral vessels, according to my conception, is quite different. They also contain a greater or lesser quantity of water, according to the activity of transpiration and the amount procurable from the soil or from the neighboring reservoirs (the pitted vessels), but unlike the pitted vessels, they are surrounded by a living, non-lignified, nonlacunose parenchyma, and there is no free access of air to their interior, but, on the contrary, so far as we can judge from the anatomical structure, this part of the plant has been developed with special reference to keeping it out. When the spirals are not full of water, they probably contain rarefied air. The very thin walls of these spiral vessels bear on their inner face lignified annular or spiral thickenings, which are probably of great service in strengthening the delicate walls, so that they may be strong enough to resist the collapsing tendency of the vacuum pull due to the osmotic pressure, and yet remain thin enough to readily allow water to filter into them or out, as the case may be. Such, roughly sketched, is the nature of the bundle, the xylem part of which contains 5 or 6 spirals and from 12 to 15, or more pitted vessels. The cucumber stem, exclusive of the hypocotyle, usually contains 9 such bundles, the 5 larger ones forming an interrupted ring or cylinder in the central part of the stem, and the four smaller ones alternating with the larger ones nearer the surface of the stem, the fifth bundle of the outer series being usually wanting in this species. These bundles are separated from each other by thin-walled, living cells which are nearly iso-diametric. The central portion of this parenchyma and that between the bundles, may be designated as medullary tissue, and that farther out as cortical parenchyma, although all of this fundamental tissue bears chlorophyll, and is used to store starch in prior to the development of the fruit. Outside of the bundles, and not far from the surface of the stem, is a compact tissue formed of numerous elongated, thick-walled, flexible, strengthening cells. These are the bast fibres, forming collectively, the stereomatic sheath. This sheath is several rows of cells thick and forms an broken or nearly unbroken cylinder in the young stem, but is afterwards ruptured longitudinally into a dozen or more strands by the growth of the stem in thickness. Between these strands of stereome, the cortical parenchyma finds its way to the epidermis, except where the latter is specially strengthened by sub-epidermal strands of collenchyma. The stem appears to have so developed as to secure every advantage to be derived from a combination of lightness with flexibility and strength.

To indicate the movement of the water in the stems and leaves, various aniline stains were tried, e. g., eosine, soluble nigrosene, methyl green, methyl orange, acid fuchsin, etc. Eosine proved by far the most satisfactory, none of the other stains moving with anything like the same rapidity, and some of them causing copious precipitates in the vessels. None of the substances in the sap of the cucumber vessels cause any precipitate with eosine, and it is probable that dilute solutions of this substance, while clearly poisonous to the plant, move with the same rapidity as pure water, at least at first.

1. UPWARD MOVEMENT OF ONE PER CENT. EOSINE WATER

THROUGH CUT STEMS.

(No. 9). This vine was 215 centimeters long and bore a number of small leaves and 17 large ones, 10 of which averaged 20 cm, in breadth. March 21, 2:30 p.m. The stem near the earth was cut under water and put at once into 1 per cent. eosine water. 2:43 p.m. The stain is now distinct in all of the principal veins of a leaf only 15 cm. from the end of the stem, i. e., it has passed up the stem a distance of two meters in less than 13 minutes, probably in 10 to 12 minutes. 2:47 p. m. The red stain is now distinct in the veins of the small undeveloped uppermost leaves of the stem. 3:25 p. m. Slight droop of the foliage, but much less than in No. 10 (a similar vine in 10 per cent. eosine water). Foliage decidedly less red than that of No. 10. 4:35 p. m. Leaves drooping very decidedly. The leaves of No. 10 are flabbier and redder, but much less fluid has passed up the stem. 5:10 p. m. About 21 cc. of the eosine water has passed up the stem in 2 hours and 40 minutes. March 22, noon. Leaves, tendrils and surface of the young fruits reddish. The stain does not make its way readily into the coiled tips of the tendrils. Many of the leaves are dry shriveled, so that they crackle on touch. Stem not shriveled. Most of the petioles are still turgid and but little stain is visible in them, except in a few toward the top of the vine. 4:00 p. m. Not nearly so red as No. 10. Stem quite green and not noticeably shriveled. The stem of No. 10 in the 10 per cent. eosine has shriveled decidedly to-day. March 23, 12:25 p.m. About 10 cc. of the stain has passed up the stem since last night. 4:30 p. m. About 10 cc: of the stain has gone up the stem since the last record. March 25, 12:30 p.m. About 20 cc. of the stain has passed up the stem since the last record. Most of the leaves are crisp dry, but the terminal ones are still moist, although shriveled and soft like old rags, the parenchyma being yellow and the veins bright red. Most of the petioles are bright red, and all of them are limp and hang straight down; the stem has shriveled and become reddish, except the

Distilled water containing Dr. Grübler's “ Eosine Soluble in water."

submerged part, which has kept its turgor and resists diffuse staining better than the parts in the air. The plant is dead. March 26, 2:40 p. m. About 12 cc. of the eosine has passed up the stem since yesterday p. m.

In this plant over 40 cc. of the eosine water passed up the stem during the first 24 hours, and in the next four days an additional 45 cc., part of which after the plant was dead.

Vine No. 1 which was 188 centimeters long, also took up the eosine water after it was dead. This absorption of the stain continued long after the leaves had become dry-shriveled, and did not entirely cease until all parts of the bright red stem became bone-dry. This vine was under observation 14 days, during which time about 150 cc. of 1 per cent eosine water passed up the stem, only 57 cc. of which went up during the first 494 hours.

(No. 25). This was a young vine, measuring 100 centimeters above the cut surface. It bore 17 leaves, the largest 6 averaging 13 cm. in breadth. March 28, 11:56 a. m. The stem was cut under water and put at once into an alkaline eosine water, made by putting 1 gr. eosine into 100 cc. of io caustic soda (the solution stood in the laboratory over night and became darker colored). 12:01 p.m. The red stain is distinctly visible in the veins of all the leaves, even the uppermost ones, i. e., it has gone straight up a distance of one metre in 5 minutes. It is sunny and windy, and transpiration is active. The dry bulb registers 22° C.; the wet bulb 17.3° C. 12:10 p. m. The foliage begins to droop. 12:40 p. m. Foliage wilting very badly. 2.10 p. m. About 5 cc. of the stain have passed up the stem. The lower leaves have begun to crisp at the margin. March 29, 2:30 p. m. About 7 cc. of the stain have passed up the stem since the last record. The blades of the leaves are crisp and the petioles are bright red. March 30. Fluid quite dark; an additional 4 to 5 cc. has gone up the stem. Stem and petioles much brighter red than yesterday. April 3, 11 a. m. The entire stem and all of the petioles have become extremely bright red, the eosine water (20 cc. of it) having continued to pass up the dead stem since the last record. The leaves appear to have taken up no stain since March 29. They are not now crisp, but feel limp like old rags. The veins are bright red, but the parenchyma is yellowish-white. The surface of the stem feels moist and stains the fingers red when rubbed.

Similiar results were obtained with a 1 per cent. solution of sodium chloride containing 1 per cent. eosine. Acidulated waters (1 per cent. citric acid and 1 per cent. hydrochloric acid) also passed up the cut stems rapidly and in large quantity, and after the stems were dead. The 1 per cent. hydrochloric acid proved much more poisonous to the plant than did the 1 per cent. citric acid. Similar experiments were made with hydrant water. In the latter, after a few days, the plants reduced their foliage to a minimum, and then lived on for many days, i. e., in case of a plant used for comparison with No. 1, until long after the latter was dead and dry.

To sum up the results of these experiments, of which the preceding are only examples, we have the following propositions:

(1). The rate of movement of the water current in cucumber stems during active transpiration is at least 10 to 12 meters an hour. (2). Absorption of water and transpiration continues in dead stems for some time, i. e., until they have become dry. (3). Large quantities of fluid passed through the cut stems during the first few days. (4). When the cut stems were plunged into water tinged with eosine, sufficient of this stain was taken up to color all the tissues of the plant bright red, including parenchyma, sclerenchyma, collenchyma and epidermis; the first parts to show the stain being the spiral vessels.

(To be Continued.)

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