HARDWICKE'S SCIENCE-GOSSIP. 



149 



of true roots ; the structure of the stem is very simple. 

 In the foliose section, it consists of an elongated 

 parenchyma, thickening externally, thus forming a 

 cortical layer passing gradually into the central 

 ground tissue. 



No Cryptogam possesses greater interest for the 

 microscopist than the Liverwort, which is found on 

 almost every damp rock, or wall, and even on the 

 borders of well-kept gravel paths. 



First, a part of the frond, or thallus, should be 

 washed to free it from particles of soil, or grit ; then 

 having selected a portion of the outer edge, make a 



a single layer. The amphigastria are distinct 

 from the root hairs, and consist of a series of 

 cells, arranged like a necklace. In some of the 

 other trans, sect, will be noticed the root-hairs 

 (fig. 93) or rhizoids. Stain the section with magenta 

 and observe their structure, the darker parts in 

 the figure represent thickenings, which project 

 inwards of the cell-wall and arranged in a spiral 

 series ; the young rhizoids display the arrangement 

 well. 



Select a bit of an older thallus, and make a long. 

 sect, to trace the peculiar and interesting lozenge- 



Fig. 94. — Thallus, with Antheridia. 



Fig. 95. — Section through young Antheridia. 



Fig. 96. — Stalk bearing Archegonia. 



Fig. 97. — Arcliegonium Marcluintia, magnified. 



sketch of it as (fig. 87), so as to understand its 

 dichotomous branching. The midrib is very con- 

 spicuous, and continually divides in a forking or 

 dichotomous manner. Then take the clean thallus, 

 the upper portion, and cut several sections, betwixt 

 a carrot, passing them from the razor blade, with a 

 fine camel-hair pencil, into a watch glass containing 

 water, then mount several so as to have them at hand 

 beneath a cover slip. Now search for the amphi- 

 gastria. With a little care, they will soon be seen. 

 No. 1 (fig. 90) is the amphigastria ; 2, cellular tissue 

 of the thallus, and 3, epidermis, the latter formed by 



shaped divisions, as fig. 88. The epidermis may 

 be stripped off for the purpose, but I find it better 

 to cut a thin section ; No. 1 is the lozenge-shaped 

 division ; 2, stomata in the centre, and 3, a lighter 

 band separating the division. Again cut several 

 trans, sect, of the thallus, as before (fig. 91). To 

 observe the peculiar stoma, note it well ; it takes a 

 little trouble to secure a nice specimen. No. 1 is 

 the stoma, forming an opening, composed of five 

 parts, like the bricks in a chimney. The lower cells 

 contract or expand, according to the state of the 

 atmosphere, to regulate the moisture, Sec. ; 2, 



