200 PREPARATION AND MOUNTING 



been chosen ; but it requires rather more power than the 

 Yallisneria. This plant is very common in many parts of 

 the country, a great number of our ponds and streams being 

 literally choked up by it. In the Chara vulgaris and two or 

 three of the Nitellae, &c., this phenomenon may also be seen 

 with no preparation except plucking a part from the stem 

 and laying it upon a slide, as with the Anacharis. In using 

 the Frog-bit, the outer part of the young leaf-buds must be 

 taken to obtain the best specimens for this purpose ; but a 

 section of the stem will also show the circulation, though not 

 so well. The plants before mentioned are all aquatic, but 

 the same movement of the globules has been observed in 

 several kinds of land plants ; as in the hairs upon the leaf- 

 stalks of the common groundsel ; but these do not show it 

 so well, nor are they so easily managed as the preceding. 



Many microscopists who are not fortunate enough to be 

 in the neighbourhood of these plants (indeed the Yallisneria 

 is a foreign one) grow them in jars ; so a few remarks as to 

 the treatment they require will not be out of place. The 

 Vallisneria requires a temperature not lower than 55 or 

 60, and even a higher degree than this renders its growth 

 quicker; and no great change must take place : the more 

 equable the temperature the more healthy will the plant be. 

 A glass jar should be taken, having an inch or two of mould 

 at the bottom, which must be pressed down closely, and the 

 plant must be set in this. Water must then be gently 

 poured in, so as not to disturb the mould. As this plant 

 nourishes best when the water is frequently changed, 

 Mr. Quekett recommends that the jar should be occasionally 

 placed under a tap of water, and a very gentle stream 

 allowed to fall into it for several hours, by which means 

 much of the confervoid growth will fee removed and the 

 plant invigorated. The Anacharis may be rooted in the 

 earth like the Vallisneria, but a small detached piece may be 

 thrown into the jar of water and there left until wanted. 

 For months the circulation will be well shown by it, and it will 

 probably grow and increase. It is also very healthy in an 



