422 BOTANICAL GAZETTE [NOVEMBER 
probable errors in the use of the method for studying the rate of photosynthesis 
as affected by carbon dioxide concentration. 
Part III deals with the effect of short periods of darkening of varying 
cellular spaces and thereby drawing water into these spaces. The longer the 
period of darkening the greater the contraction. On the basis of these results 
Kniep develops in part IV a method for determining the minimum light 
intensity necessary to produce oxygen elimination into the intracellular spaces, 
or to give an excess of photosynthetic gas exchange over the genre: 
exchange. Itis 2.8 candle meters. This paper deals mainly with methods 
are to be used later in answering various questions in bio 
WILLIAM CROCKER. 
Life histories in Laminariaceae.—In his recent investigation of Saccorhiza 
bulbosa, SAUVAGEAU! found that germinating zoospores behave quite at vari- 
ance with results reported by other workers. Instead of a protonema, as found 
by Wrxi1aMs,5 Drew,’ and Kian,’ he found that the erect plant is devel- 
oped directly, and also® that Saccorhiza shows heterogamy and distinct alter- 
nation of generations. 
ter swimming about for a time, the zoospore comes to rest, rounds out, 
and develops a membrane, becoming an “embryospore.’’ Subsequent behavior 
determines whether the embryospore is to be a male or female gametophyte. 
In the latter case the embryospore doubles its diameter, multiplies its chroma- 
tophores without division of the nucleus, and in a short time a tube puts out, 
of about the same diameter as the embryospore, though its length may greatly 
exceed the diameter; into’the tip of this tube the entire contents of the embryo- 
spore migrate. Finally the membrane is ruptured and there escapes a single 
naked uninucleate mass, slightly elongated in form, which remains attached . 
to the mouth of the empty embryospore tube. This naked mass, which is the 
UVAGEAU, C., Sur le développement et la biologie d’une Laminaire (Saccorhiza 
ey Compt. end. Acad. Sci. 160:445-448. 1915; 161:740-742. IQI5. 
Wits, J. L., Germination of the zoospore in the Laminariaceae. Rept. 
British Ass. Adv. Sci. “@Bradiord) Igo0. 
, The zoospores of the Laminariaceae and their germination. Rept. 
British Ass. hae Sci. (Dundee) 1912. 
rEw, G. H., The reproduction and early development of Laminaria digitata 
and L, keecharbic: ‘hia. Botany 24:177-190. 1910. 
7 KiLi1an, K., Beitrige zur Kenntnis der Laminarien. Zeitschr. Bot. 3:433-494 
Igtt. 
8 SAUVAGEAU, C., Sur la sexualité hétérogamique d’une Laminaire (Saccorkiza 
bulbosa). Compt. Rend. Acad. Sci. 161:796-799. 10915. 
