1908] CURRENT LITERATURE 471 
following groups; Equisetales (an Equisetites), Filicales (a species each in Marat- 
- tiaceae, Osmundaceae?, Schizaeaceae, and Cyatheaceae?), Bennettitales . 
Williamsonia), Ginkgoales (a Baiera), and Coniferales (a Pagiophyllum); i 
addition to these, there are four unassigned cycadophytes and two species of 
Podozamites. The collection from Turkestan includes approximately the same 
range of forms, adding a species of Dipteridinae and eight species of unassigned 
Filicales, but showing no Marattiaceae or Schizaeaceae; representing Gink, 
goales by two species of Ginkgo; and adding three Coniferales. In conclusion, 
the relations of these floras to those of other regions are shown by a table; and 
also the wide distribution of some of the species. Among the striking facts are 
the existence of so many species for a considerable time during the Mesozoic; 
the general uniformity in the composition of both the Rhaetic and Jurassic 
floras in different parts of the world; and the remarkable paucity of cycadean 
remains in the Turkestan beds.—J. M. C 
Light perception.—ALBRECHT has examined a large number of the endemic 
plants of northern Germany for the organs of light perception (lenticular epi- 
dermis, ocelli, etc.) to which HABERLANDT attributes the capacity of distin- 
guishing differences of light intensity. He finds? the organs very rare, and 
when they are present, nearly as common on the under as on the upper surface 
of the leaf, though it is clear that to the illumination of the upper surface alone 
is due the exact placing of the leaf in the fixed light position. No difference 
appeared in the adaptation of sun and shade leaves to the perception of light. 
He adduces again the experiments made by coating leaves with water, gelatin, 
and oil, as evidence against HaBERLANDT’s theory. After the reading of the 
paper, HABERLANDT spoke of the faulty methods in all the latter experiments, 
describing a mode of coating a part of the leaf with water and leaving the other 
part dry. On stimulating the two parts with light from different directions, the 
dry part was always the controlling one, even though the light was much weaker. 
-Haserianvt considers these experiments (to be detailed later) quite decisive. 
‘It may be pointed out, however, that other factors than light are here ao 
and that the weight of evidence is clearly against HABERLANDT. —C.R 
Invertase of the date.—VrNSON has studied further® the invertase of greenr 
and ripe dates, in an endeavor to discover the reason for its inextractability from 
the green fruit. He finds that the tannin present does not make it insoluble, 
nor can it be extracted from ground pulp, so that impermeability of the cell 
‘membranes is excluded. He proposes the theory “‘that green date invertase and 
possibly other endoenzymes are held in an insoluble combination by some con- 
stituent of the protoplasm. In some cases this combination may be broken 
-; Arprecut, G., Ueber die Perception der Lichtrichtung in den Laubblattern. 
_ Ber. Deutsch. Bot. Gesells. 26a:182-191. 1908. 
_ 8 Vinson, A. E., The endo- and ektoinvertase of the date. Jour. Am. Chem. 
Soc. 30:1005-1r020. 1908. Cf. earlier paper, Bot. GAZETTE 43:393- 1907. 
