b. B. homogeneous sac; the granular less transparent protoplasm; the small round vacuoles. Draw. The intermixed Torula. Note their size and number. Hold a bit of the mycelium between two pieces of carrot, and cut a thin vertical section with a sharp razor: mount in water and examine with low and high power. b. The submerged hyphæ. C. Small branched threads hanging down from the under surface of the mycelium: repeat the observations 2. a. a. a. The aerial hyphæ and conidiophores. Tease out in water a bit from the surface of one of the greenish patches; observe the difficulty with which water wets it. Examine with low and high power. Note; a. The primary erect hypha. B. Its division into a number of branches. γ. The division of the terminal branches by constrictions into a chain of conidia. d. The conidia. a. Their Size (measure). Form; spherical. Draw. Structure; sac, protoplasm, vacuole. b. Stain with magenta and iodine. C. Treat another specimen with potash. e. The germination of the Conidia, and building up of the Mycelium. a. Sow some conidia in Pasteur's fluid in a watch-glass ; protect from evaporation, and watch the development of the mycelium (examine the surface with a low power); then the formation of aërial hyphæ; finally the production of new conidia. b. [Sow Conidia in Pasteur's fluid in a moist chamber, and watch from day to day; note the formation of eminences at one or more points on a conidium; the elongation of these eminences to form hyphæ; the branching and interlacement of the hyphae.] B. MUCOR MUCEDO. I. 2. 3. Place some fresh horse-dung under a bell-jar and Snip off a few of the hyphae with a pair of scissors, Examine with obj. a. The hyphæ. a. Their size; they greatly exceed the hyphæ of Penicillium both in length and diameter. B. Their structure; homogeneous sac, granular protoplasm, vacuoles: septa absent except close to the sporange. γ. Treat with iodine and magenta; the protoplasm is stained. 8. Treat another specimen with Schulz's solution; the wall is stained violet. C. C. а. obj. Their size and form. Their structure. α. The homogeneous enveloping sac covered by irregular masses of calcic oxalate. B. The granular protoplasmic contents: unsegmented in some; divided into a great number of distinct oval masses (ascospores) in others. 7. The projection into the sporangial cavity of the convex septum (columella) which separates the hypha from the sporange. S. The collar projecting around the base of the columella of burst sporangia. Stain some with iodine; others with Schulz's solution. The ascospores. Crush some ripe asci by gentle pressure upon the cover-glass. Examine with obj. The size of the ascospores (measure). Their form; cylindrical and elongated. Their structure. Stain with iodine and magenta. VI.. STONEWORTS (Chara and Nitella). THESE water-weeds are not uncommonly found in ponds and rivers, growing in tangled masses of a dull green colour. Each plant is hardly thicker than a stout needle, but may attain a length of three or four feet. One end of the stem is fixed in the mud at the bottom, by slender thread-like roots, the other floats at the surface. At intervals, appendages, consisting of leaves, branches, root-filaments, and reproductive organs, are disposed in circles, or whorls. In the middle and lower parts of the plant these whorls are disposed at considerable and nearly equal distances; but, towards the free upper end, the intervals between the whorls diminish, and the whorled appendages themselves become shorter, until, at the very summit, they are all crowded together into a terminal bud, which requires the aid of the microscope for its analysis. The parts of the stem, or axis, from which the appendages spring are termed nodes; the intervening parts being internodes. When viewed with a hand-magnifier the internodes exhibit a spiral striation. In Chara, each internode consists of a single, muchelongated cell, which extends throughout its whole length, invested by a cortical layer, composed of many cells, the spiral arrangement of which gives rise to the superficial marking which has been noted. And this multicellular structure is continued from the cortical layer, across the stem, at each node. The stem therefore consists of a series of long, axial cells, contained in as many closed chambers formed by the small cortical cells. The nodes are the multicellular partitions between these chambers. The branches are altogether similar in structure to the main stem. The leaves are also similar to the stem, so far as they consist of axial and cortical cells, but they differ in the form and proportions of these cells, as well as in the fact that the summit, or free end, of the leaf is always a much-elongated pointed cell. The branches spring from the re-entering angle between the stem and the leaf, which is termed the axilla of the leaf; and, in the same position, at the fruiting season of the plant are found the reproductive organs. These are of two kinds, the one large and oval, the sporangia or spore-fruits, the other smaller and globular, the antheridia. Both, when ripe, have an orange-red colour, and are seated upon a short stalk. If a growing plant be watched, it will be found that it constantly increases in length two ways. New nodes, internodes, and whorls of appendages are constantly becoming obvious at the base of the terminal bud; and these appendages increase in size and become more and more widely separated, until they are as large and as far apart as in the oldest parts of the plant. The appendages at first consist exclusively of leaves and root-filaments (rhizoids), and it is only when these have attained their full size, that branches, spore-fruits and antheridia are developed in their axillæ. Sometimes rounded cellular masses appear in the axilla of the leaves, and, becoming detached, grow into new plants. These are comparable to the bulbs of higher plants. If the innermost part of the terminal bud, which constitutes the free end of the axis, or stem, be examined, it will be found to be formed by a single nucleated cell, |