42 A HALF-HOUR WITH THE 



the hairs of the common stinging-nettle, represented 

 at tignre B>Sa. 



The hairs constituting the down or " pappus " of 

 compositoiis plants assume a variety of forms The 

 seed or fruit of the common groundsel has a beau- 

 tiful crown, given at figure 245, in plate 8. The 

 papiDus of the dandelion appears notched, as seen 

 at figure 2i6. The burdock has a cottony hair, 

 while the goatsbeard is like a feather,-both of 

 which are represented respectively in fi^rures 2i7 

 and 248. ° 



If a hair is examined in its growing state, with 

 an object-glass of one quarter of an inch focus a 

 movement of the particles in its interior is often 

 observed. This is easily seen in the hairs around 

 tne stamens of the common Spiderwort (Trades- 

 canha Virginica). Such movements are very com- 

 mon in the cells of water plants. One of those 

 most commonly cultivated in aquavivaria at the 

 present day, the Valisneria sjjiralis, affords the best 

 example of this interesting phenomenon. In order 

 to observe this movement, a growing leaf of the 

 valisneria should be taken, and a longitudinal slice 

 should be removed from its surface, by means of a 

 sharp penknife or razor. The slice, or the sliced 

 part left on the leaf, should now be put on a slide 

 a drop or two of water added, and covered with a 

 thin piece of glass, when, after a little time, espe- 

 cially m a warm room, the movement will be ob- 

 served. This movement takes place in the little 

 particles around the sides of the cells represented 

 m figure 88b, plate 3. It may also be seen in 

 the leaves of the new water-weed (Anacharis 

 ulsmastrum), the frogbit, the rootlets of wheat in 

 the family of charas, and in the cells of many other 

 water plants. In examining some species of Chara 

 the external bark, or rind, should be removed from 



