1886.] 



MICROSCOPICAL JOURNAL. 



given us a very graphic description 

 of the phenomenon first observed by 

 Unger. In 1856 Pringsheim describ- 

 ed the true sexual propagation by oo- 

 spores, with such minuteness and ac- 

 curacy, that our knowledge of the 

 plant can scarcely be said to have es- 

 sentially increased since that time. 



Vaucheria has two or three rather 

 doubtful marine species assigned to it 

 by Harvey, but the fresh water forms 

 are by far the more numerous, and it is 

 to some of these I would call your 

 attention for a few moments this even- 

 ing. The plant grows in densely in- 

 terwoven tufts, these being of a vivid 

 green color while the plant is in the 

 actively vegetative condition, chang- 

 ing to a duller tint as it advances to 

 maturity. Its habitat (with the ex- 

 ceptions above noted) is in fresh wa- 

 ter — usually in ditches or slowly run- 

 ning streams. I have found it at 

 pretty mucli all seasons of the year, 

 in the stretch of boggy ground in the 

 Presidio, bordering the road to Fort 

 Point. The filaments attain a length 

 of several inches when fully devel- 

 oped, and are of an average diameter 

 of -^\^ (-004) inch. They 

 branch but sparingly, or not 

 at all, and are characterized 

 by consisting of a single long 

 tube or cell, not divided by 

 septa, as in the case of the 

 great majority of the fila- 

 mentous algcE. These tubu- 

 lar filaments are composed 

 ofanearlv trans- 

 parent cellulose 

 wall, including 

 an inner layer 

 thickly studded 

 w i t h bright 

 green granules 

 of chlorophyll. 

 This inner layer 

 is ordinarily not 

 noticeable, but 

 it retracts from the outer envelope 

 when subjected to the action of cer- 

 tain re-agents, or when immersed 

 in a fluid differing in density from 

 water, and it then becomes distinctly 



Fig. 3. — Formation of gonidia 



visible, as may be seen in the engrav- 

 ing (Fig. 3) . The plant grows rapid- 

 ly, and is endowed with much vital- 

 ity, for it resists changes of tempera- 

 ture to a remarkable degree. Vatiche- 

 ria aflbrds a choice hunting ground 

 to the microscopist, for its tangled 

 masses arc the home of numberless 

 infusoria, rotifers, and the minuter 

 Crustacea, while the filaments more 

 advanced in age are usually thickly 

 encrusted with diatoms. Here, too, 

 is a favorite haunt of the beautiful 

 zoophytes. Hydra viridis and H. 

 vulgaris^ whose delicate tentacles 

 may be seen gracefully waving in 

 nearly every gathering. 



After the plant has attained a cer- 

 tain stage in its growth, if it be atten- 

 tively watched, a marked change will 

 be observed near the ends of the fila- 

 ments. The chlorophyll appears to 

 assume a darker hue, and the gran- 

 ules become more densely crowded. 

 This appearance increases until the 

 extremity of the tube appears almost 

 swollen (Fig. 3). Soon the densely 

 congregated granules at the extreme 

 end will be seen to separate from the 

 endochrome of the filament, a 

 clear space sometimes, but not 

 always, marking the point of di- 

 vision. Here a septum 

 or membrane appears, 

 thus forming a cell 

 whose length is about 

 three or four times its 

 width, and whose walls 

 completely en- 

 close the dark 

 green mass of 

 crowded granules. 

 These contents 

 are now gradually 

 forming them- 

 selves into the 

 spore or ' gonidi- 

 um ' as Carpen- 

 ter calls it, in dis- 

 tinction from the true sexual spores, 

 which he terms 'oospores.' At the 

 extreme end of the filament (which 

 is obtusely conical in shape) the 

 chlorophyll grains retract from the 



