234 PHYSIOLOGY [Bot. Absts., Vol. IV,. 



than to differences in degree of senescence. The explanation of these results may be that the 

 parent plant was not old enough to show measurable senescence compared to its rejuvenated 

 offspring; that the venation character is not correlated with age in this species; or that re- 

 juvenescence is not a function of sexual reproduction. The author inclines to the latter in- 

 terpretation, holding that the "undifferentiation" which is the essential feature of rejuvenes- 

 cence occurs in the reduction of the organism to a unicellular embryo, and is independent of 

 the stimulus, sexual or otherwise, which initiates growth. — A new method for clearing and 

 staining leaves is described. — G. S. Torrey. 



1556. Findeis, Marie. Uber das Wachstum des Embryos im ausgesaten Samen vor der 

 Keimung. [On the growth of the embryos in sown seeds before germination.] Sitzungsber. 

 K. Akad. Wiss. Wien (Math. -Nat. Kl.) 126: 77-102. 2 pi. 1917.— See Bot, Absts. 4, Entry 

 987. 



1557. Gertz, Otto. Panachering hos Mercurialis perennis L. En morfologisk, anatomisk 

 och mikrokemisk studie. [Variegation in Mercurialis perennis L.] [Swedish, with German 

 resume.] Bot. Notiser 1919: 153-164. Fig. 1-28. 1919.— The studies were carried out in the 

 Beechwoods of Torup, Skane, Sweden, from 1907 to 1917. The partly chlorophyll-free leaves 

 were confined to specimens growing in a very restricted area, and it seemed as if these speci- 

 mens had developed by budding from the rootstock of one original mother-plant, though a 

 few normal specimens were growing in the clump. The variegation consisted sometimes in a 

 chlorophyll-free marginal zone, 2 mm. wide of variable length, sometimes in larger or smaller 

 white blotches. The epidermal cells were much larger in the normally developed portion of 

 the leaves, the ratio being on the upper side 2.6:1 and on the lower side 2.7:1. The shape of 

 the cells was often changed, and the cell-walls, normally very sinuate, often became straight 

 in the white fields, especially in the region of tension between the different colored fields. 

 The stomata, which are found on the lower surface, were often irregular or only partly devel- 

 oped in the white fields. There were also differences in the thickness of the blades, the nor- 

 mally developed fields being thicker, the ratio being 1.5:1 up to 2.1:1. The palisade cells on 

 the upper surface had become depressed in the white fields and more like the epidermal cells. 

 The parenchyma-cells and the vessels showed also some differences. The white fields lacked 

 as a rule starch, except in the cells of the stomata. In cultures of chlorophyll-free pieces in 

 glucose-solution, starch was formed, however. The white fields contained less albumen. 

 Mercurialis perennis gives excellent material for studies of Molisch's "kalium-karotin" reac- 

 tions. Reference literature, 7 articles. [See Bot. Absts. 3, Entry 2126.] — P. A. Rydbcrg. 



1558. Hart, E. B., and H. Steenbock. Maintenance and reproduction with grains and 

 grain products as the sole dietary. Jour. Biol. Chem. 39:209-233. Charts 1-13. 1919. — 

 Grains and their products used as the sole articles of diet proved insufficient for maintenace 

 (growth was not experimented on) and reproduction in the animal experimented on. Broad 

 generalizations must not be made from experiments on a few species. — G. B. Rigg. 



1559. Illick, J. S. When trees grow. Amer. Forest. 25:1386-1390. 9 fig. 1919.— See 

 Bot. Absts. 4, Entry 437. 



1560. MacDotjgal, D. T. Growth in organisms. Science 49:599-605. 1919. — In this 

 address, delivered before the Pacfic Division of the American Association for the Advance- 

 ment of Science, at Pasadena, June 19, 1919, the writer considers the subject according to the 

 following brief: (1) The development of an organism from the spore or embryonic stage in- 

 cludes the processes of auxesis or enlargement and of differentiation. (2) Living matter is 

 conceived to be composed mainly of pentosans and albumins or albumin derivatives. (3) 

 The principal and characteristic substances of the two groups are practically non diffusible,, 

 and hence come together only as an intimate mixture in a colloidal condition. (4) Growth 

 of living matter consists of hydration with accompanying swelling and of accretion of solid 

 matter. (5) The hydration of the substances belonging to the two main components is 

 affected in an opposite manner by hydrogen ions, and is variously modified by temperature and 



