82 BOTANICAL GAZETTE [JULY 
PirtTrer® has published his fifth contribution dealing with new or note- 
worthy plants from Colombia and Central America. Under various subtitles 
15 new species are described, representing 12 genera, Bombacopsis oe 
bacaceae) being a new genus. There is also a revision of Brownea and Brown 
opsis (Caesalpiniaceae), as represented in Panama, Colombia, and Veneaiie! 
TAKEDA” has described a new genus (Dysmorphococcus) of algae, which 
resembles externally Trachelomonas. The material was found in a sma 
stagnant pond in Richmond i Surrey, England. 
VaN ALDERWERELT VAN ROSENBURGH,” in his seventh paper on new or 
interesting Malayan ferns, has published as new species or with new names 
42 species of ferns, representing 21 genera, and also 3 new club mosses.— 
J. M.C. 
Temperature and growth rate.—LeEITCH,” working in the plant physiology 
laboratory of the University of Copenhagen, has done an excellent piece of 
work upon the effect of temperature on the rate of growth of the main root of 
Pisum sativum. Short experimental periods were used to avoid errors due to 
changing rate in the course of the grand period of growth. The period of 
maximum growth rate (root 5-1o mm. long) was also chosen. It was impor- 
tant in determining methods of experimentation that diffuse light or change of 
temperature, as such, does not modify the rate of growth of this organ. The 
temperature coefficient, Q1, is as follows for temperatures between o° C. 
and 28° C. 
Range of Peneabitne Range of Temperature 
temperature coefficient temperature coefficient 
o-10° C 8.25 12-22°C. 2.67 
2-12° pea 6.28 T4394 2.44 
4-I4'....-. Cee eo Se ees 
16° sae 2.92 16-20": 2.23 
S186 ot. 3.24 1S-ae" ae | 
10-90"... 4S! 2. 
The temperature coefficient is typically van’r Horr’s only between 10° and 
29° C., while below 10° C. the coefficient exceeds the van’r Horr value of 
2 to 3. This means little regarding the nature of the growth process, for the 
coefficient often greatly exceeds 3 in monomolecular reactions in vitro. In 
* Pirtrer, Henry, New or noteworthy plants from Colombia and oo 
America. V. Contr. U.S. Nat. Herb. 18:143-171. pls. 57-80. figs. 10. 1916. 
AKEDA, H. sopeconiacuamaice variabilis, gen. et sp.nov. Ann. Botany 30:151- 
16. 
_ 156. figs. 15. 191 
- LDERWERELT VAN RosENBURGH, C. R. W. K.., <i or interesting 
Malayan ferns. VII. Bull. Jard. Bot. Buitenzorg 20: 1-28. pl. 4. 1915. 
* LeITcH, I., Some experiments on the influence of duaain on the rate of 
growth in Pisum satioum. Ann. Botany 30:25-46. figs. ro. pl. 1. 1916 
