1902] CURRENT LITERATURE 83 
. frequently poor in chlorophyll. Griffon agrees with Overton ® that the autumnal 
4 colors are due to excessive carbohydrate concentration in the chlorenchyma. 
He also holds with Bonnier that the synthetic power of xanthophyll is rela- 
tively inconsequential. The influence of various external factors en carbo- 
hydrate synthesis is well presented but must be omitted here, except to state 
that Griffon finds that chlorophyll formed in the dark (as in conifer seedlings) 
acts normally. In this connection it may be noted that Bouilhac # has found 
4 chlorophyll in Nostoc by spectroscopic tests and has succeeded in observing 
’ the formation of chlorophyll in this form in the dark, when it is fed with 
ydrates, such as glucose. Griffon thinks that the development of 
POL in the dark is in all cases associated with a supply of reserve 
s. 
In his second paper Griffon measured the amount of carbohydrate syn- 
thesis in solar light which has traversed one or more leaves. That certain 
light rays are cut off in traversing leaves is well known, but few previous 
attempts have been made to measure synthesis. Nagamatz used the starch 
method, which is now known not to be accurate. Griffon uses the gas 
method, and finds that active synthesis takes place in the second leaf even 
where light has traversed a thick and densely green leaf like Hedera or 
Laurus ; in the case of such plants, where a leaf is shaded by two leaves, 
respiration commonly exceeds synthesis. The synthethic energy of the 
second leaf varies, according to differences in amount of chlorophyll and 
chlorenchyma, and to undetermined factors (probably specific chlorophyll 
differences), between one-half and one-forty-eighth of that in the leaf which 
receives unmodified solar rays. In diffuse light the synthethic energy of the 
mone leaf is of course still less. To summarize, respiration generally 
— synthesis where light has traversed two leaves in the sunlight or one 
leaf in the shade. , Oe : : 
| ei Linsbaner © has investigated the transparency of a number of leaves with 
_& fee: of Wiesner's photometric methods. Only the more refrangible rays” 
iia Weed Leaves vary widely in the amount of light that they transmit, — 
_ a saves of Cytisus and Cornus transmitting only 0.0003 of the light offered 
— while shade leaves of Fagus transmit 0.02. In general, shade leaves 
Pea more light than do sun leaves. The same species and even — 
inne ioe “ as J. C. Miller showed) shows wide variations, the shade : 
th x egy transmitting seven times as much light as the sun leaf; per- 
Bo a ee: di fer i nees are due in part to variations in the amount of the | 
fon EE eee | 
Comp: Rend. 126: 1583-1586. 1898. 
~entralb. Beihefte ro: 53-89. 1901. 
