424- Mr Gustav Mann's 



vigorously growing material alone should be used for studies, 

 and not the thread lying at the bottom of the vessel. 



Strassburger's and Detmer's methods for cultivating 

 Spirogyra answer both very well. Strassburger's method is 

 shortly this. The material is placed in shallow vessels with 

 opaque walls, to prevent unilateral light acting on the plant, 

 but at the same time the vessel is placed in a light place, 

 protected from the direct action of the sun, and a room 

 towards the north is to be preferred. From time to time 

 pieces of turf soaked in the following nutrient fluid : — 



Water, . . . .100 ccm. 



Potassium nitrate, ... 1 grm. 



Sodium chloride, . . . 2 » 



Calcium sulphate, . . . 2 » 



Magnesium sulphate, . . 2 " 



Calcium phosphate, . . 2 " 



are placed in the vessels containing river or spring water. 



Detmer's formula for a nutritive solution is : — 

 1 grm. CagNOg, . "\ 



0-25 „ KCl, . . ( in 1 litre of distilled 



0-25 „ MgS04, . j water. 



0-25 „ KH2PO4, . J 



I find that if 1-| litre of distilled water instead of 1 litre be 

 taken, that Spirogyra will grow more vigorously. 



The vessel I like best for cultivating Spirogyra is one 

 made of glass and covered with white tissue paper, about 

 18 inches deep by 18 inches broad (if broader ones are to be 

 had they should be taken) ; it is filled with fresh spring 

 water up to 3 inches from the top, then a current of carbon 

 dioxide is passed through the water for five minutes, the 

 material placed into the water and exposed to bright 

 daylight. The carbon dioxide I prepare in the usual way 

 with nitric acid and pieces of marble, and it is purified by 

 being passed through a lye of caustic potash. The purified 

 gas is conducted to the vessel wnth water by means of an 

 india-rubber tube, into the end of which a glass tube is fitted, 

 drawn out into a fine point. Whenever the gas begins to 

 escape by the glass tube, the latter is pushed to the bottom 

 of the vessel and moved about, to allow the gas bubbles to 

 come in contact with as much water as possible. 



