112 THE PLANT WOELD 



eiglits of an incli, but the third side was more seriously injured. 

 Here the strip of bark was entirely separated from the wood, break- 

 ing the cambium cells, and thus preventing the wound from healing. 

 The strip of bark, however, remained attached at top and bottom. 

 Some of the cells in the separated portion must have been un- 

 injured, as they began to form new wood. The bark curved in 

 around this new growth and formed an independent body nearly 

 round, with the exception of the ridge on the inner side. 



This tree is growing near the north end of Cedar Mountain, Hart- 

 ford Conn. — H. S. Clark, Hartford, Conn. 



Cleaning Desmids. 



The method to be described is particularly applicable to material 

 obtained from mountain bogs containing submerged plants of Sphag- 

 num, among which specimens of the genera Micrasterias, Ereastrum, 

 Closterium, Penium, and others aboimd. To collect desmids from this 

 source a good plan is to squeeze the Sphagnum into a wide-mouthed 

 bottle. But the majority of desmid gatherings appear amenable to the 

 same method of cleaning. 



The apparatus required consists of one or two shallow porcelain 

 saucers or photographic dishes, an old pomatum pot being useful among 

 the number, and a tapered glass tube with a rubber cap, for which pur- 

 pose the " filler " of a stylographic or fountain pen answers admirably. 

 A gauze strainer of a coffee pot is useful for straining out any large 

 pieces of dirt, the stuff left behind being examined for filamentous des- 

 mids. 



The strained material is run into one of the porcelain dishes, and 

 after a short interval — not more than half a minute — the dish is in- 

 clined to one side, a gentle rocking motion being given at the same 

 time. If there are any desmids in the gathering, they will be seen to 

 collect in a bright green line or patch at the edge of the receding water 

 when they may be readily picked up with the pen-filler in a state of 

 almost purity. On working the water round the edge of the dish, the 

 desmids may be drawn into green patches in almost any desired part 

 of the vessel, and one lot after another picked up till there are none 

 left worth troubling about. 



As the desmids are removed I transfer them to the pomatum pot, 

 when a drop of Zenker's fixative suffices to fix them. A repetition of 

 the rocking process enables the desmids to be once more collected and 

 taken up in the pen-filler, while, if any flocculent matter was picked up 

 with the desmids in the first separation, this may often be left behind 

 with a considerable portion of the fixative. The desmids are now trans- 



