144 BOTANICAL GAZETTE [FEBRUARY 
otropically) in darkness, and give a very characteristic geotropic reaction, having 
abundant statolith starch. P. epiphylla generally does not grow in darkness. 
Neither these two nor Lophocolea bidentata are geotropic in light. ‘The behavior 
in darkness of P. epiphylia, the two eed of Lophocolea, and the sporogone 
of Aneura must be considered as purposeles: 
The researches appear to strengthen a statolith theory of geotropic per- 
ception.—C. R. B. 
Photosynthesis. —UsHER and Priestiy, having shown in a previous paper*® 
that CO, may be decomposed in plants independently of enzymic or “vital” 
activity provided the products (H.02 and H’'COH) are removed, have now 
devised an arrangement by which photolysis of CO, can be produced in vitro.*® 
By covering gelatin plates, or even water, with a very thin uniform layer of chloro- 
phyll deposited from solution, and placing the glass plate or the shallow dish of 
water carrying the film in a vessel with CO, and illuminating it, they found for- 
maldehyde produced and were able to recover identifiable quantities. By 
making up the gelatin with an aqueous solution of a catalase, the hydrogen 
peroxid also produced was decomposed with the evolution of O2, 2°° being 
obtained in one case. The chlorophyll was gradually bleached, in harmony 
with the view that it acts as a sensitizer and is destroyed in the process of pho- 
tolysis. Synthesis of H'COH into carbohydrate was found in the earlier paper to 
dependent on the healthy condition of the protoplast, and feeding experiments 
have already shown that H'COH when supplied in very dilute form can be con- 
densed by green plants if illuminated. The authors painted the white petals 
of Saxifraga Wallacei with chlorophyll, and floated them on water charged with 
CO, in light. . In the course of a day they were found to contain starch. Thus 
they secured photosynthesis by a different (though inefficient) arrangement of 
the mechanism of a green leaf. 
Further study was made of photolysis of CO. in the presence of uranium 
salts. They have direct evidence of the production of formic acid (which also 
is produced under some conditions in the plant as an intermediate product in the 
reduction of CO,), but they were unable to isolate and identify formaldehyde. 
These papers record a most important step in solving the problems of photo- 
synthesis.—C. R. B. 
Vascular anatomy of cycads.—Two years ago MATTE published his thesis on 
the vascular anatomy of the cycads,:? in which he presented in great detail, with 
copious illustrations, the vascular anatomy of the leaves and flowers in represen- 
tative species of all the nine genera; and of the seedlings of Dioon edule, Cycas 
ts UsHER, F. L., and Priestiy, J. H., A study of the en a of carbon 
assimilation in green plants. Proc. Roy. Soc. London B. 77:369-376. 1905- 
16-_The mechanism of carbon assimilation in green plants: Pe photolytic 
decomposition of carbon dioxid in vitro. Idem 78:318-327. 1906. 
17 Matte, H., Recherches sur l’appareil libero-ligneux des Cycadées. pp. 233- 
bls. 16. figs. 264. 1904. 
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