26 



American Quarterly Microscopical Journal. 



growth of a young and thrifty filament under a magnifying 

 power of 200 diameters. For the first hour observations were 

 taken every five minutes ; during the second, every ten min- 

 utes, after which the time varied. The first column represents 

 the time of measurement, and the second the length of fila- 

 ment. 



TABLE SHOWING RAPIDITY OF GROWTH. 



From these data it will be seen that growth for the first 

 hour averaged 6.5 mm. ; for the second, 7.64 mm., and for the 

 third about 6 mm. ; this, it will be remembered, under a mag- 

 nifying power of 200 diameters. Growth during the remainder 

 of the day averages a considerable less, but judging from the 

 appearance of the plant at 8 o'clock the next morning, I think 

 that growth had taken place as rapidly as when the first mea- 

 surements were taken. The branches shown were given off 

 at 10.07 and 10.42 o'clock, and averaged 7.8 mm. per five min- 

 utes. The time required for a plant to develop fruit from the 

 zoospore varies greatly with varying conditions. A mat of 

 mycelium, from which the specimen was taken, developed 

 fruit in four days, but this time was rather long when com- 

 pared with other observations made on the same germs, con- 

 sidering that the mycelium was already well developed. In 

 one case zoospores were placed upon a slide with a small frag- 

 ment of a fly, the first sporangium opened in about thirty hours, 

 and the second one on the same filament eight hours later. I 

 have not yet made any satisfactory observations on the second 

 mode of reproduction in this genus, but according to the best 

 authorities on this group, it is in principle very similar to that 

 described further on, under the genus Achlya. The number 

 of times that this unsexual form may be produced without 

 the intervention of sexual reproduction, or in a single vegeta- 

 tion period, I have not been able to ascertain. A series of ex- 

 periments bearing partially upon this point, and showing a 



