1907] CURRENT LITERATURE ^ 159 



Influence of external conditions on geotropic response. — A timely paper by 

 Bach^^ records some valuable conclusions, of which perhaps the most important 

 is that the length of the reaction time cannot be used as a measure of the amount 

 of stimulation. The minimum presentation time found in a variety of species 

 was two minutes^ as compared wath fifteen minutes found by Czapek. Czapek's 

 figure has thus far been w^idely accepted, but the lower values of the author are 

 apparently good. The length of the plant is a factor if the plant is less than 

 medium, in which case the reaction-time is lengthened. Temperature is a potent 

 factor, even variations of 14-35°. Such variations have been regarded by Czapek 

 as impotent, but the opinion was based on the behavior of different material. 

 Either regular or irregular shaking are indifferent factors. Other important con- 

 ditions tried were duration of stimulation, centrifugal force, positional deviations. 

 The paper shows the guiding hand of Fittixg, whose service is acknowledged. 



Raymond H. Pond. 



Young sporophytes of Lycopodium. — Miss WrGGLESWORTH^'=' has investi- 

 gated the structure of sporelings of L. complanatum and L, clavatum, the material 

 being obtained from Dr. Bruchmann and consisting of tw^o sporophytes of each 

 species. The first root may show monarch, diarch, and triarch arrangement in 

 the same plantlet, the phloem occupying the center of the stele and extending 

 between the xylem groups to its periphery. The roots arise endogenously near 

 the apex of the stem and either pass out directly or downward through the cortex. 

 At the base of the stem the vascular strands are continuous with those of the first 

 root, and a fusion of two or of all three of the xylem strands occurs. The xylem 

 strands take a very irregular course, fusing with one another and subdividing in 

 the lower part of the stem. The upper part of the stem shows a triarch or tetrarch 

 arrangement of xylem with central metaxylem, generally connected with two or 

 more groups of protoxylem. — J. M. C. 



Embryology of Rhytidophyllum. — CooK^' has investigated the embryology 

 of Rhytidophyllum {R. crenulatum and R. tomentosiim), a genus of Gesneriaceae, 

 the material being Cuban. The ovulate archesporium is a single hypodermal 

 cell, which usually functions directly as a megaspore. The embryogeny is of 

 the well-known Capsella type, differing only in certain features of dermatogen- 

 formation and in the contributions of the hypophysis. The embrj^o encroaches 

 upon both endosperm and nucellus, and in the mature seed is invested only by 



the integuments. — J. M. C. 



^9 Bach, Heixrich, Ueber die Abhiingigkeit der geotropischen Prasentations- 

 und Reaktionszeit von verschiedenen ausseren Faktoren. Jahrb. Wiss. Bot. 44:57- 

 123. 1907. 



^^ WiGGLESWORTH, Grace, The }oung sporoph}^es of Lycopodium complanatum 

 and Lycopodium clavatum. Annals of Botany 21:211-234. pL 22. 1907- 



=^' CoOK, Melville T., The embryology of Rhytidophyllum. Bull. Torr. Bot. 

 Club 34:179-184. pL 10. 1907. 



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