Carnivorous Plants details of structure. They are unicellular hairs with the bases embedded in a raised mass of epidermis and underlying parenchyma. They taper from the base gradually to the sharp tip, and the cuticle is raised to form folds or ridges, beginning at or near the base and converging on the apex, where they gradually fade away. These ridges are more pronounced on the hairs of the conductive surface, and are much weaker to scarcely distinct on the hairs of the detentive surface. rapidly, o.oi gram of fibrin being completely digested in 1.3 cc. of fluid in 2 hours.In the part with acid added "partial solution was noted at the end of 9 days, complete solution at the end of 50 days." S. minor. -Experiments were done in the field. No digestion occurred in 30 days (trikresol present) in the absence of acid or alkali, but it did occur when either acid or alkali was added to the fluid, but less vigorously in the alkaline, than in the acid medium. This species therefore stands in contrast to the others aforementioned. S. psittacina. -Field observation showed that fluid was being secreted in the pitchers, but in such small amounts that it had to be collected by dilution with water (0.5 cc. in each of 50 pitchers free of insects).The results were inconclusive, but indicated that a protease is present which is active in the presence of acid. Sarracenia purpurea. -The secretion in this species is very small in amount, being found as beads of moisture on the walls. Experiments were done by flushing the pitchers, emptying, and adding 10 to 15 cc. of water to each pitcher. After some days this was removed and tested. The fluid thus obtained showed an ability when alkaline to digest fibrin to a marked extent in 8, 24, 72, and 87 hours (4 samples), and completely in 42, 48, 120, and 135 hours, respectively. Three other experiments gave positive results in 42 and 87 hours.In acid, the results were equivocal. Sarracenia
I nevertheless feel urged to insist that the only way to know what stomata are doing, and to know the relation between their condition and the diffusion of matters into and out of the leaf, is to determine these quite independently, and above all to know exactly what the condition of the stomata is. To do this we must see the stomata, not one or a few, but many, and on different leaves.On this point Copeland (1902, p. 330) is correct. All of the methods above referred to may properly be used for certain purposes, as, e. g.,to determine roughly the ratio of transpiration of the upper and lower surfaces of the same leaf, but for exact work on stomata some method of direct observation was needed.Immediate microscopic study of the stomata on a leaf in situ, as has been carried on by Kohl (1895 and earlier) and others, was practically, though not wholly, impossible in both of the plants studied. To study the living stomata in epidermis removed alone, or in thick tangential sections of the leaf, and mounted in water, offered difficulties and sources of error which could not be overcome.Air bubbles, which cling so persistently, prevent accurate measurement;and it would have defeated my purposes to have used the method of mounting the epidermis or sections in boiling water, which, upon standing, will take up 24 THE PHYSIOLOGY OF STOMATA.the air by solution (Copeland, 1902). Furthermore, stomata, when mounted for observation in water, may, as others, including myself, have found, suffer sudden changes in contour (von Mohl), a possibility fatal to my object.Indeed, I found that invariably the stomata of Verbena ciliata suddenly enlarge their transverse (tangential) measurements when water reaches them.This may be determined without very great difficulty if a piece of epidermis is mounted* for microscopic observation first without the addition of any medium. After observing the size of certain stomata, these, upon running water under the cover, will be found to open wider. Thus, 5 closed stomata in different pieces of epidermis taken at 6 p. m. opened so that their pores became 6 micra broad. In another case, the outside transverse measurement of 4 neighboring stomata, all of which were closed, were taken. These were, in micra, 28, 26, 24, and 27. Upon the addition of water, the measurements were 34, 32, 28, and 30, respectively.By means of a stop-watch the rate of opening may be determined with but fair though sufficient accuracy. Thus a stoma opened o to 7 micra in somewhat less than 3 seconds. It will be appreciated that, to mount epidermis in water and, after placing on the stage, then to examine the stomata, might result in hopeless error.Nothing can be said of stomata mounted in water, as regards their condition in situ, unless it is known that placing in water does not effect them in the least, which is unlikely in any case.Again, the removal of epidermis has been objected to on the ground that this results in a release of tensions which are responsible in part for the size of the stomatal openings. I have suspected...
The genus Roridula has two species, the leaves of both of which are armed with numerous glands secreting a "balsam"-like exudate, whereby many insects are captured, simulating in this the behavior of Drosera, Drosophyllum and Byblis. But as Marloth held, these plants are not carnivorous.Living "commensally" on both species are at least five different insects, three crab-spiders and two capsids (true bugs). All these can move about freely on the Roridula plants without danger of capture; they gain their livelihood by sucking the juices of freshly captured insects.The structure of the glands of these plants and the nature of their secretion are described.The immunity of the insects above mentioned from capture is attributed to the character of the surface of the resinous secretion, to the spiny surface of the insects, which prevents the presentation of extensive surfaces for adhesion and to the ability of the insects to negotiate their environment. The argument is not held to be conclusive but suggestive; and the matter is worthy of further study.
The Comparative Embryology of the Rubiaceae II. DESCRIPTIVE Vaillantia hispida Vaillantia is a small genus of the Galieae containing only two annual species, indigenous to the Mediterranean region. The plants are monoecious ; the flowers are borne in threes supported by a single broadened spiny stalk. Of the three the middle is pistillate, the two lateral staminate. The three-flowered peduncles are in four vertical rows alternate with the four rows of leaves. The regularity and perfect radial symmetry of the species studied render it easy to section a growing tip so as to cut all the ovules of two opposite rows longitudinally. The material was obtained at the Botanical Garden at Berlin. The Origin and Development of the Nucellus At the period of the development of the pistillate flower when the four corolla lobes have met above the hollowed out receptacles and overarch the stamens, which are as yet merely rounded knobs at the angles of the sinuses of the corolla, four elevations lying in the same vertical plane make their appearance near the base of the ovary. The outer two of these are ridge like, and by their mode of growth meet later in the transverse plane, fuse; extend upwards to form the two styles, and downward to form a partition which divides the originally unilocular ovary into two chambers. The two others are papilliform and lie on either side of the center of the floor of the ovary.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.