16 



ANALYTICAL CLASS-BOOK OF BOTANY. 



94. THE THALLUS. The leaf-like body which is 

 called a frond, in the Seaweeds and Ferns, in the Lichen, 

 Liverwort and Mushroom tribes, takes the name of 

 THALLUS. This, like the frond, is a confusion or blend- 

 ing together of leaf and stem. The bed of fibres from 

 which mushrooms spring is called a thallus, and the same 

 name is given to the leaf-like patches that cover old 

 wood, walls and rocks with growths of Lichens, better 

 known as Gray Moss. A common Lichen of our stone 

 walls is shown at fig. 9. In this we see the spreading 

 thallus and the specialized cells of reproduction, in various 

 little cup-like forms, which most of us, perhaps, have 

 noticed in the living plants of this family. They are 

 sometimes prolonged into the form of a wine-glass, and 

 not unfrequently are of a bright scarlet. Country chil- 

 dren know them well, and call them fairy-cups. 



95. CAULESCENT FORMS. A species of Lichen, which 

 hangs in long and tangled masses from old forest trees, 

 especially in damp places near the coast, makes the wood 

 appear as if hoary with age. It often exhibits the rudi- 

 ments of a stem. This, however, is more distinctly 

 attained in the Reindeer Moss, fig. 10, which in Lapland 

 grows more than a foot in height. In seaweeds the 

 stem is often greatly extended, sometimes attaining to 

 more than two hundred feet in length. At fig. 7 is one 

 of these plants, in which the stem is the leading idea of 

 development. But this organ, like the Leaf, in all these 

 Orders, is but imperfectly defined. 



96. The Orders that have been mentioned namely, 

 Fungi, Algae and Lichenes contain plants of the Mush- 

 room, Seaweed and Lichen tribes, which imbibe their 

 food by all parts of their surface indiscriminately. But 

 with the next advance, in the Liverworts (Order Hepat- 

 icte), we meet with some important changes. The repro- 

 ductive cells become more strongly marked, and the dis- 

 tinctions of leaf, stem and flower are more clearly de- 

 fined. The very color shows that the leaf is attaining 

 somewhat more nearly to its normal state, by the secre- 

 tion of chlorophylle (65), and the whole structure appears 

 greatly advanced. At fig. 13 is seen a species of Liver- 

 wort (Marcantia), with a stalk appearing to spring out 

 of its spreading thallus, which somewhat resembles an 

 Oak-leaf. At the summit of the stalk is a flower-like 

 organ, in which the spores are contained. At the right 

 hand corner of the thallus is a cup-form receptacle, in 

 which small, roundish cells are deposited. By these also 

 the plant is multiplied, and they bear a striking analogy 

 to the buds and bulbs of higher plants. 



97. REPRODUCTIVE ORGANS OF LIVERWORTS-. These 

 in Marcantia distinctly shadow forth the stamens and 

 pistils of higher forms. At fig. 17 is a highly magnified 

 representation of the AiraiEpaDUM, or little sac con- 

 taining the fertilizing spores, which it is in the act of 

 discharging from its ruptured surface. At fig. 16 is the 

 pistillate Sporangium, or sac containing the mother- 

 cells of the same plant. It is surrounded by several 

 filamentous processes, composed of cells in linear series, 

 as at c. The involucre, J, is rounded, and swelling at the 

 base like an ovary, while its prolongation represents a 

 style and stigma. A very curious addition to this appa- 

 ratus is seen at fig. 19, which represents one of the 

 SPIRAL ELATERS, or elastic threads, contained in the 

 sporangia. This appears to be a very important part of 

 the operating forces. It has several spores, or mother- 

 cells, attached. These spiral threads are extremely 

 sensitive to the presence of moisture, and under its influ- 

 ence they expand elastically, and scatter the spores. 



98. MOSSES. In all the foregoing we find no proper 

 roots, the fibrous portions resembling that organ being 

 useful only in fixing the plant to the surface on whioH 

 it grows ; and they are produced, with almost equal free 

 dom, from all parts of the plant. An actual epitome of 

 the perfect plant first appears in the Mosses (Order 

 Musci), which not only send up a regular stem, sym- 

 metrically clothed with leaves, but they also send down 

 delicate little root-like processes that pierce the soil, and 

 doubtless, to some extent, perform the proper functions 

 of the root, by absorbing nutriment, although the plant 

 also takes up nourishment through its whole expanded 

 surface. 



99. Here, too, the reproductive organs are distin- 

 guished .by a regular apparatus of very complex structure, 

 a superficial view of which may be seen at fig. 20, where 

 is represented a Moss, with its leafy though not erect 

 stem, and its fruit elevated on slender stalks. The 

 hooded veil which covers the fruit both of Liverworts 

 and Mosses is called a CALYPTRA. At fig. 1 1 the spo- 

 rangia are magnified, so as to show the teeth in the ca- 

 lyptra, whose lid incloses the germinating cells. In 

 the early stages of growth, the calyptra closely envelopes 

 the sporangium ; but being detached by the expansion of 

 the inclosed tissue, it is carried upward, and forms a 

 hood, cowl, or lid, which closes the extremity until the 

 mother-cells are ripe for dispersion, when it opens a pas- 

 sage through its pores, as seen at fig. 1 1. 



100. CELLULAR AND FIBROUS PLANTS. All the 



To what order Jo Seaweeds belong? Leaf of Seaweeds called whut ? Leaf 

 of the Lichen, Liverwort and Mushroom tribes? What important changes are 

 met with in the Liverworts? What is the sac of mother- cells called? Describe 



Marcantia. Its reproductive apparatus. To what Order do Liverworts 

 belong ? What changes found in the Mosses 1 Hood of Mosses, what called ? 

 Describe. Order of the Moss tribe. 



