1900] MICROSCOPICAL JOURNAL. 103 



nummuloides in salt-waters also and becomes Melosira 

 borreri and others most likely. 



Thus we can have a spherical form formed as Cyclotella 

 and when attached in chains, Melosira. Cyclotella-like 

 forms al«o occur in salt-water attached to sea-weeds as 

 Podosira, single or double or in chains. As Coscinodis- 

 cus it appears, not spherical of course, but as flattened 

 spheres and when it is viewed on the side view, as it is 

 called, looks like discs. 



As students of the Bacillaria are commonly observers 

 of Diatoraes merely, looking at the prepared plants or what 

 they are called, the disc is a common form seen and Cosci- 

 nodiscus becomes a disc-like form. 



Two common forms appear in the spring when, or near- 

 ly when, the Cyclotella in fresh-water makes its appear- 

 ance. These are the first to appear (Nitzschia) and com- 

 monly two or three days or a week or so after Synedra. 

 These are both baccillar or rod-like forms. The Nitzschia 

 are not so rod-like as the Synedra, but both are common 

 the Nitzschia perhaps most common, and in still water, 

 whilst the Synedra is in running water. Nitzschia ap- 

 pears in positions where the stratum is only slightly moist, 

 as for instance on the green scum of flower-pots, wliich 

 is made up of unsized clay and is therefore porous and 

 holds the water readily. The form that occurs under this 

 circumstance is a short rod, seeming like a disc that has 

 been growing in one direction more than another, in fact 

 an oval form. It was called by Meneghini, Frustia viri- 

 dula and it was published, in 1844, in Die Kiesdshaligen 

 Bacillarian oder Diatomace by F. T. Kutzing. But it is 

 now Nitzschia frustulum. It was called Synedra frustu- 

 lum by Kutzing, 



We see how these Synedra and Frustulia and Nitzschia 

 came to be the same. Nitzschia frustulum is extremely 

 common as has been said on the porous red-clay flower- 

 pots. It Appears in this climate, Newark, N. J., in the 



