4 o8 



BOTANICAL GAZETTE 



[NOVEMBER 



tube; in fact, in some genera these hairs seem to serve rather as a guide to the 

 pollen tube. The fusion of the polar nuclei is tardy. The antipodals are 

 always more than 3 in number, and in some genera very many more. The 

 most striking feature of the ovule is the "hypostase" of Van Tieghem, which 

 is a clearly differentiated group of cells beneath the embryo sac, whose thin 



walls give the lignin reaction to stains. 



immediately 



beneath the embryo sac and sometimes deep in the chalaza. Its function is 

 doubtful. The author raises the question whether it is not a distinct dis- 

 advantage in shutting off water conduction to the embryo sac. 



In connection with seed development the author followed the changes in 

 the tissues of the 2 integuments, finding that the inner integument contributes 

 chiefly to the testa, but its persistent innermost layer separates from the testa 

 and becomes a thin pellicle completely covering the embryo. In some of the 

 genera in connection with seed formation, tracheae are developed in the periph- 

 ery of the nucellus, connecting with the strands of the raphe and traversing 

 the whole length of the nucellus. The author suggests that this is comparable 

 to the tracheal nucellar mantle which characterizes the seeds of some of the 

 Cycadofilicales. This feature has not been discovered before in the seeds of 

 living plants. — J. M. C. 



Tree growth. — MacDougal 2 * has issued a preliminary report describing 

 briefly an instrument for recording the variations in diameter of tree trunks. 

 Records extending over several months have now been made of individual 

 trees of Fraxinus arizonica y Pinus chihuahiiana, P. radiata, Quercus agrifolia y 

 Fagus grandifolia, and Platanus occidentalism 



Shreve 26 has added to these data a preliminary report of determination 

 made on some stumps of Pinus radiata. The maximum increase in diameter 

 for 10 years was 14 inches, while growth in height of 10 ft. for trees 12-15 inches 

 in diameter has been known. — Geo. D. Fuller. 



A new atmometer. — Bates 27 has devised a new atmometer which is said 

 to have very nearly the same relation to wind and radiant energy as do the 

 leaves of trees. A flat metallic chamber is constructed with a layer of moist 

 linen between the upper and lower plates. The upper plate not only protects 

 from rain, but also, possessing a blackened surface, absorbs radiant energy 

 freely, while the lower plate is perforated to resemble the stomatal surface of 

 leaves. Experiments have shown that the evaporation from this instrument 

 follows the transpiration from small coniferous trees very closely. — Geo. D. 



Fuller. 



^MacDougal, D. T., The dendrograph. Cam. Inst. Wash. Year Book for 

 1919. 18:72-78. 1920. 



26 Shreve, Forrest, Stem analysis and elongation in shoots of Monterey pine. 

 Cam. Inst. Wash. Year Book for 19 19. 18:88-89. 1920. 



27 Bates, C. G., A new evaporimeter for use in forest studies. Mo. Weather 

 Rev. 47:283-294. figs. 3. 1919. 



