198 Hunting for Diatoms. 



diatoms accumulating at the bottom until the present thickness 

 was attained. You will observe that the endochrome has been 

 removed by long rotting, and the entire mass is now composed 

 of the pure white siliceous valves. Pray also observe that 

 this richness in silex suits the cereal crops growing over it, but 

 does not seem to furnish much nutriment to the potatoes and 

 turnips. 



The adjacent peat beds may also be examined, for fre- 

 quently rare Diatomacese are found in the turf which is cut for 

 fuel. 



The dark, hair-like mass growing on the woodwork of this 

 sluice-gate, is a nice pure gathering of Schizonema neglectum, 

 the frustules arranged in regular rows in the interior of the 

 long filaments. 



Before leaving this pond let us pull out a mass of the 

 Myriophyllum, which seems rusty in colour. Well ! here is a 

 medley of forms, but the gathering is worth bottling up, owing 

 to the abundance of Amphipleura pellucida. 



The clear ditch by the roadside is a likely place for such 

 forms as Pleurosigma attenuatum, Spencerii and lacustre, Nitz- 

 schia linearis and tenuis, Surirella ovata, Navicula elliptica and 

 Cymbella maculata. 



The yellow mass attached to plants a little further on is 

 Cyclotella operculata, Amphora oralis and Nitzschia sigmoidea, 

 while the brown covering on the Anacharis is Gomphonema 

 tenellum, dicliotomum and curvatum. The stones in the running 

 beck, issuing from the clear spring close by, are covered with 

 long, yellowish-brown streamers, which are well worth collect- 

 ing. Take them out very gently, for they are very fragile and 

 likely to drop again into the water. The species is the beau- 

 tiful Meridion cirndare, with Melosira varians. 



At the bubbling spring itself, which forms the head of the 

 streamlet, the sand, which is tossed and heaved about by the 

 ascending water, seems tinted of a brown colour. Let us 

 secure some of the sand, when we shall find the brown colour 

 is caused by a dense parasitic growth of Odontidium Harrisonii 

 quite pure. 



Further on the dark brown streamers must be collected, for 

 here are two species of Fragillaria, Capucina, and viresccns, 

 mixed with Diatoma elongatum. The stones and aquatic plants 

 are likewise covered with a dense brown coating of Synedra 

 radians, and Ulna, species found in almost every clear water- 

 ditch. 



The boggy place where the plants are coated with a yellow 

 coating of the oxide of iron, is not to be passed without col- 

 lecting a little of the light flocculcnt surface mud. This will 

 be almost sure to yield some fine diatoms, such as Oa/rrvpyhdis- 



