230 M. Marc Micheli on some Recent 



The specimens of limestone analyzed by Dr. Ehrenberg 

 were brought from Gyzeh, on the left bank of the Nile, and 

 from Mokattam, near Cairo, on the right bank. It was com- 

 pact, the small Foraminifera serving as cementing-matter 

 among the Nummulites of which the rock is mainly composed. 



The figured Foraminifera of plate xxiii. bear evidence, in 

 the truthful engraving of their somewhat rough, partly ob- 

 scured, and occasionally broken condition, to their having 

 been closely cemented and much mineralized by carbonate of 

 lime in their fossil matrix. 



[To be continued.] 



XXIV. — On some Recent Researches in Vegetable Physiology. 

 By M. Marc Micheli. 



[Continued from p. 155, and concluded.] 



II. 



The study of the phenomena of which the interior of cells 

 is exclusively the tlieatre, of the transformations which are 

 manifested there, and of the substances which they contain 

 has also produced some works which deserve notice, and in 

 the first place the researches of M. Schroeder * upon the 

 " spring period of the maple." The author has paid at- 

 tention to all the successive phases presented by the develop- 

 ment of the vegetation, from the ascent of the sap to the 

 moment when the expanded leaves begin to decompose car- 

 bonic acid. This is one of those complete and conscientious 

 works which, even when they do not contain any very novel 

 results, are nevertheless very useful to read and consult ; but 

 it is difficult to give a clear notion of them in a few words. 



A glance at the course followed by M. Schroeder will show 

 the great number of facts which group themselves within a 

 framework such as he has adopted. 



The first part is entirely devoted to the study of the sap, 

 its ascent, and its composition. The maple, under the lati- 

 tude of Breslau, " loeeps " for about a month ; the sap rises 

 gradually to a certain level, whence it descends again by de- 

 grees, in proportion as the development advances. Holes 

 pierced in the trunk at different heights enabled this sap 

 to be collected daily ; and very numerous analyses keep us 

 informed of the smallest variations in its composition. It 

 always contains sugar, a transitory product of the transforma- 

 tion of the starch accumulated in the tissues during the pre- 



* " Friihjalirsperiode des Ahoms," Pringsheim's Jahrb. vii, p. 261. 



