456 BOTANICAL GAZETTE [JUNE 
cotyledons, such as Dracaena. Contrary to the usually accepted view, the 
author finds that cambial activity is present not in the pericycle but in the inner 
layers of the cortex. Cell divisions in the pericycle are confined to the points 
where lateral roots make their appearance, and this growth may have been 
confused by other investigators with the true secondary growth in the cortex. 
The second part of the paper is devoted to an account of the so-called ‘‘ Aussen- 
scheide,’’ a zone of more or less Haaiies cells found in the inner cortex of 
many monocotyledonous roots. This zone is not a real secondary tissue, 7. ¢., 
produced by the division of eek ia though it may assume the power 
of secondary growth. This zone is considered to be equivalent to the secondary 
tissues discussed in the first part of the paper. Several suggestions are offered 
as to the function of the “Aussenscheide,”” varying with the habits of the plant 
in which it occurs. Naturally the mechanical function seems to be the most 
common one.—M. A. CHRYSLER. 
. Morphology of Cucumis sativus.—TILLMAN?! has investigated sporogenesis 
and embryogeny in the cucumber. The most interesting items reported are 
as follows: the presence of two integuments that elongate greatly and invest 
the remarkable beak-like prolongation of the nucellus; the somewhat irregular 
development of the embryo; and an haustorial enlargement of the pollen tube 
on its passage through the long nucellar beak. e fusion of the unequal polar 
nuclei was seen, but no case of double fertilization was observed —J. M. C 
Enzymes of Polyporus.—Butirr’? finds in the juice of P. squamosus the 
following: laccase, tyrosinase, amylase, emulsin, a protease, lipase, rennetase» 
and coagulase; but negative results were obtained by tests for pectase, maltase’ 
invertase, trehalase, and cytase. Yet the fact that it destroys the wood of Acer 
pseudoplatanus indicates the presence of cytase and possibly hadromalase.— 
Limiting factors——An illuminating paper on Optima and limiting factors 
has been published by Dr. F. F. BLackMan,?3 which it behooves every physiol- 
ogist toread. The argument shows, and it is sustained by the results of research, 
that much physiological experimentation has been falsely interpreted —C. R. B. 
Photosynthesis extra vitam.—Maccuiatr replies?4 to BERNARD,?5 criticiz- 
ing his methods, maintaining that photosynthesis does occur in vitro, and stating 
certain modifications of the process. He makes a weak case.—C. R. B 
21 TILLMAN, Opa I., The embryo sac and embryo of Cucumis sativus. Ohio 
Nat. 6: 423-430. pls. 29-30. 1906 
22 BULLER, A. H. R., The enzymes of Polyporus squamosus Huds. Annals of 
Bot. 20:50-59. 1906. 
23 Annals of Botany 19: 281-295. 1905. 
24 Maccaiati, L., Altri fatti e nuovi argomenti sull’ assimilazione fotosintetica 
fuori dell’ organismo ees le richerche del dig. Dr. Ch. Bernard. Nuovo Giorn. 
Ital. 12: 461-4 1905. 
25 Bot. GAZETTE 41:157. 1906. 
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