No. 1, August, 1920] PHYSIOLOGY 133 



945. Stalfelt, M. G. Uber die Schwankungen in der Zellteilungsfrequens bei den 

 Wurzeln von Pisum sativum. [Variations in the frequency of cell division in the roots of Pisum 

 sativum.] Svensk. Bot. Tidskr. [Stockholm] 13: 61-70. 1919. — In experiments on the action 

 of weak electric currents on roots of Pisum sativum the author observed a periodicity in cell 

 divisions. The number of dividing cells was counted in 10 sections from each root. Since 

 nuclear division is sensitive to external conditions these experiments were carried out in dark- 

 ness at a constant temperature. The frequency of cell division in each root is periodic. The 

 intensity of division shows distinct maxima and minima. The rhythm is independent of daily 

 periodicity and therefore not synchronous in different roots. Periods of active division are 

 succeeded by rest periods. The duration time of the phases of cell division is estimated in 

 percentages of the total time required for division as follows: prophase, 32.78 per cent, meta- 

 phase, 36.96 per cent, anaphase 19.39 per cent, telophase, 10.95 per cent. — Pea roots of the 

 same age and length were placed in a spiral of fine silver wire which carried 3 milliamperes at 

 low potential. Roots were left in spirals 1 to 10 hours and examined for frequency of cell 

 division. Roots so treated showed the maximum number of dividing cells. The maximum 

 rate of division continues for several hours after stimulation. The author believes that the 

 passage of the current acts as a stimulus which breaks the autonomous period of cell division. 

 — R. B. Harvey. 



946. Stout, A. B. Intersexes in Plantago lanceolata. Bot. Gaz. 68: 109-133. 2 pi. 

 1919— See Bot. Absts. 3, Entry 1517. 



MOVEMENTS OF GROWTH AND TURGOR CHANGES 



947. Cocks, E. Making a plant tie itself into a knot. Sci. Amer. 121:579. 1 fig. 1919. 

 — A geotropic response. — Chas. H. Otis. 



GERMINATION, RENEWAL OF ACTIVITY 



948. Andronescu, Demetrius Ion. Germination and further development of the embryo 

 of Zea Mays separated from the endosperm. Amer. Jour. Bot. 6: 443^52. 1 pi. 1919. — 

 Embryos of corn (with their scutella) were separated from their endosperms and germinated 

 in water and in various culture media, of which 1 and 2 per cent sucrose solutions produced 

 the best results. The young plants thus obtained were considerably smaller than those pro- 

 duced by whole kernels, but were otherwise identical with them. When the scutellum as 

 well as the endosperm was removed, growth was very much reduced and the seedlings were 

 unable to develop far.— Seedlings grown from embryos only and those grown from whole 

 kernels were transplanted into soil and the plants obtained were essentially similar, except 

 that the former were somewhat smaller than the latter. The author concludes that in germi- 

 nation and development the presence of endosperm is not essential, but is beneficial. — E. W. 

 Sinnott. 



949. Anthony, Stephen, and Harry V. Harlan. Germination of barley pollen. Jour. 

 Agric. Res. 18: 525-536. PI. 60-61. 1920.— The pollen of barley (Hordeum) germinates readily 

 within a period of 5 minutes when proper moisture and temperature conditions are afforded. 

 The moisture relation is extremely critical. In the experiments, moisture was supplied from 

 a fragment of green leaf tissue placed in a dry mount of pollen in a Van Tieghem cell. Slight 

 drying of pollen causes collapse of the cell wall and free moisture causes rapid swelling and 

 bursting. — In field experiments the receptivity of the stigma was found to extend over several 

 days. Pollen used in 8 successive stages of development (from immature to that obtained 2 

 days after dehiscence of the anther) gave satisfactory percentages of fertilization only when 

 taken from anthers that were dehiscing or had only very recently opened. — No satisfactory 

 means was found of storing barley pollen. A "study of the conditions governing fertilization 

 in nature shows that conditions unfavorable to fertilizations are also unfavorable to progress 

 in the development of pollen and vice versa. In this way natural fertilization is secured." — ■ 

 D. Reddick. 



BOTANICAL ABSTRACTS, VOL. V, NO. 1 



