16 PRACTICAL BOTANY. 



and portions of the stem of the Moss-plant on moist soil, and 

 under other favourable conditions, to induce a formation of 

 protonemal filaments by direct outgrowth of cells of those parts. 



SPHAGNUM (the Bog -Moss}. 



XVIII. Take a plant of any native species of Sphagnum, and 

 observe with the naked eye, or with a pocket lens 



1. The brown stem on which are inserted 



2. Leaves of simple form. 



3. The lateral branches, with fasciculate branches of higher 

 order, which in their turn bear leaves : these branches assume 

 two distinct forms 



a. Stronger branches, of larger size, which have their apices 

 directed upwards. 



b. Weaker branches, which are deflexed, and are usually found 

 in close apposition to the main axis. 



KB. Owing to the main axis being thus closely covered by the 

 weaker deflexed branches, the leaves borne by the main axis may 

 escape observation : to prevent this, the branches should be 

 entirely removed, and the leaves will then be easily seen in their 

 normal position : it may further be noted on observing the leaves 

 carefully that the lateral branches are not axillary, but are in- 

 serted alongside of a leaf, and that a fascicle of branches is 

 associated thus with every fourth leaf of the main axis. 



Nothing comparable to the protonema of other Mosses is to be 

 found in Sphagnum, except under certain conditions of germina- 

 tion of the spore. 



XIX. Cut transverse sections of the main axis of a plant of 

 Sphagnum, and mount in weak glycerine or glycerine jelly : 

 examine under a low power, and observe 



1. At the periphery of the section two or three irregular layers 

 of cells with thin walls, and no cell-contents : lying internally to 

 these is 



2. A dense brown band of tissue which merges gradually into 



3. A massive central pith, of comparatively large cells, with 

 thin cell-walls and but little protoplasm. 



Examine the peripheral tissues under a high power : round 

 holes will be observed in the cell-walls as seen in surface view, 



