24 



THE AMERICAN MONTHLY 



[February, 



moist rocks, wood-work, etc., but not 

 in water. 



If we follow the life-histories of 

 some of the lower algae, we find 

 strong evidence that their complete 

 cycle is passed as unicellular plants. 

 They have been studied with great 

 patience, and it has been found that 

 some of them, under certain conditions, 

 will multiply for generations without 

 change, but under other conditions, 

 the cells will give off swarm-spores in 

 abundance. A few of them have 

 been observed to grow into filament- 

 ous plants. But I am not yet willing 

 to admit that all these simple algas are 

 sporules of more complex forms. 

 The facts stated by Paul Richter in 

 regard to Glxocystis and its cycle of 

 growth,* seem to preclude the supposi- 

 tion that this plant is a developmen- 

 tal stage of a filamentous plant. He 

 has shown a genetic connection be- 

 tween Glixocystis and several other 

 forms of equally simple structure, — 

 Glceocapsa, Cylindrocystis, Microcystis, 

 and Palmella, but no tendency to 

 further development of the individual 

 cells of Glxocapsa has been observed. 

 It seems probable, however, that the 

 cells of this plant sometimes grow in 

 sheaths, forming Sirosiphon (fig. 6,y), 

 but we may question if this is truly a 

 higher stage of development. 



Richter has also endeavored to es- 

 tablish a genetic connection between a 

 number of other genera, and he regards 

 Aphanocapsa as an intermediate form 

 between Glceocapsa and Glxothece or 

 Aphanothece. 



A short resiune of the relations 

 between some of the simpler algaj 

 according to the latest observations, 

 may prove interesting as well as an 

 aid to the memory in classifying them. 

 The two large classes of Phycochrom- 

 ophyceae, and Chlorophylophyceas, so- 

 named from the color of the cells, 

 which in the former are yellowish, 

 brownish, or dark-green, and in the 

 latter bright-green, have correspond- 

 ing genera. The naked, single cell 



* This Journal, ii. pp. 25, 52. 



plants, usually living in a layer of 

 clear, homogeneous jelly, are, in the 

 two classes, respectively Aphanocapsa 

 and Palmella. 



From these we naturally pass to the 

 encysted forms Glceocapsa and Glceo- 

 cystis already mentioned (fig. 6, V). If 

 the gelatinous investment is wanting, 

 we have C/iroococciis and Eremosp/icera, 

 and when the cells are segregated in 

 families the Pleurococciis found on tree- 

 trunks, fences etc. Glceocapsa has 

 been observed to grow into Scytonema, 

 and Sirosiphon (fig. 6,/), to which it 

 bears the same relation, in form if 

 not in fact, as Gloeocystis to Hormo- 

 spora. 



There are many forms consisting 

 of a sperical, more or less gelatinous 

 envelope enclosing numerous green 

 cells. These may be regarded as 

 derived from the gelatinous, encysted 

 forms like Gloeocystis. The filamen- 

 tous algae are undoubtedly derived 

 from simple cells which at some time 

 were caused to elongate and grow in 

 a certain direction. Perhaps the 

 transition forms, in this process of 

 developement, are to be seen in the 

 cylindrical cells of Glceothece, Aphan- 

 othece, etc. The beautiful sphere of 

 Volvox seems very complex, yet what 

 difference can we distinguish between 

 the individual gonidia of the sphere, 

 and the motile form of Proococcus with 

 its gelatinous investment through 

 which the flagella extend ? 



The study of algae is very fascinat- 

 ing, and such questions as we have 

 raised in this article indicate a wide 

 field for original investigation and 

 discovery. 



The Detection of Adulteration 

 in Food. 



BY C. M. VORCE, F.R.M.S. 

 MUSTARD. 



This condiment, of so univer- 

 sal use, is probably never obtained 

 strictly pure. The commercial article 



