summary Seasonal measurements of light‐ and temperature‐dependence of photosynthesis of the nuisance alga Cladophora glomerata (L.) Kutz were determined under laboratory conditions with algal samples collected from lower Green Bay, Lake Michigan. Photosynthesis rates were determined using oxygen difference in water circulated around the speciments. Photosynthesis reached light saturation at about 790 μmol photons m−2 S−1 (PAR) and had a temperature optimum between 28 and 31°c; maximum rates were 25–50 mg O2 g dwt −1 h‐1. These parameters varied seasonally with water temperatures. There was no evidence for a decline in photosynthetic rate with increasing temperature over the ranges used in this study. It is concluded that, in this instance, such an effect is not responsible for the mid‐season decline of this species. Other effects, such as those of respiration, photorespiration and phenology may, therefore, be important.

A backward-sloping ultrasonic wave is generated by reflection of a finite amplitude distorted wave from a pressure-release boundary. The difference between the behavior of this wave and that of a wave distorted in the usual sense is demonstrated.

The dissipationless theory for harmonic generation in an initially sinusoidal, plane, finite-amplitude wave is used as a basis for calculation of the harmonic components of such a wave in a fluid with dissipation.The assumption used is shown to lead approximately to the relationships of the Fox and Wallace theory. The result is given as a Fourier series, with graphs of the first few harmonic components for two specific cases. The series representation is valid for distances X_< L, where L is the discontinuity distance for the dissipationless case. NOTATION C'-Velocity of wave phase points. Co-Sound velocity for infinitesimal amplitudes. P-Pressure. P0-Internal (equilibrium) pressure. p-Density. p0-Equilibrium density. .. A, B-Empirical constants in the equation of state. X= Distance from origin of wave. U-Particle velocity. a--Infinitesimal amplitude absorption coefficient for the fundamental frequency component. f(n)=Factor by which a must be multiplied in order to obtain the absorption coefficient of the nth harmonic in the medium of interest. v= Fundamental frequency. L-Discontinuity distance for dissipationless case. K-X/L= Reduced distance. r= ox/r. P, (K) --Pressure amplitude of the nth harmonic wave component, measured at reduced distance K. /•(•)--Harmonic generation parameter (Fox and Wallace).

The fundamental-frequency component of a plane, finite-amplitude wave is measured in water at 5.65 Mcps by a fixed-distance pulse method giving variable-distance results. The absorption coefficient of the fundamental-frequency component of the wave is examined from the standpoint of its maximum, average, and instantaneous values. It is found that there is a maximum amount of sound-pressure amplitude that can be transmitted over a fixed path, varying as the −0.80 power of the distance. A value for the nonlinearity parameter of water is obtained, giving B/A = 6.3±0.8.

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