1906] CURRENT LITERATURE 45 
Seedlings of Piperales —In continuing his work on the structure of the seed- 
lings of certain Piperales, Hrt1+? has published results dealing chiefly with 
several species of Peperomia. The transition phenomena are described in 
detail; that is (in brief), the arrangement of the vascular tissues in the cotyle- 
donary or primary node, the transition region between root and stem, where the 
earliest tissues of the vascular system arise. The conclusion in reference to 
the primitive or reduced character of Peperomia is confirmatory of JoHNSON’s 
view that it is a reduced genus, the determining factor in reduction possibly 
being the epiphytic habit of many forms. It is also suggested that these tran- 
sition phenomena may not be such important phylogenetic criteria as has been 
assumed by some investigators, since they do not seem to be sufficiently rigid 
to withstand the influence of varying conditions.—J. M. C. 
Antipodal cells —In a long article LorscHER‘ discusses the structure and 
function of the antipodal cells of angiosperms. On the basis of their anatomy 
and physiology he finds three types of antipodals: (1) those remaining as naked 
protoplasts or free cells and functioning in the resorption of the nucellus (Orchid- 
aceae, Cruciferae, Geraniaceae; Linaceae, Papilionaceae, Primulaceae, Pol- 
emoniaceae, and Scrophulariaceae); (2) those well differentiated and forming 
a roundish cell-complex which serves to transform the foodstuffs which are 
brought to the embryo-sac (Gramineae, Araceae, Ranunculaceae, Mimosaceae, 
Cesalpinaceae, and in combination with the third type, predominant in Lili- 
aceae, Iridaceae, Zingiberaceae, Borraginaceae, and Solanaceae); (3) those, 
singly or together, having an elongated form and functioning principally as 
haustoria (most Rubiaceae).—CHARLES J. CHAMBERLAIN. 
Mechanics of secretion This problem has been attacked by LEPESCHKIN, 
who finds44 that from “unicellular” plants (Pilobolus, Mucor, Phycomyces, 
and Vaucheria are so called), as well as from the epidermal structures of green 
plants, secretion is to be referred to the unlike permeability for solutes of the 
plasma membrane in the absorbing and secreting regions of the structure. The 
process of secretion and the influence of external agents upon it agree com- 
pletely with the mathematical formulae for the energy involved, based upon 
the current theories of osmotic pressure. The permeability of the membrane 
is easily altered by external and internal influences. Whether this is character- 
istic of all semipermeable membranes or only of plasmatic membranes remains 
to be determined. The research adds some facts but leaves much yet to be ex- 
plained regarding the subject.—C. R. B 
4? Hitz, T. G., On the ES of certain Piperales. Annals of Botany 
20:160-175. pl. Io. 1906. 
43 LorscHer, P. Konrap, Ueber den Bau und die Funktion der Antipoden in 
Ko 
der PR te Flora 94:213-262. pls. I-2. 1905. 
SCH 
aactcttie der Pflanzen. Beihefte Bot, Cent. 19:409-452- 1906. 
