308 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Xerophytic Leaves of Pertya phylicoides.— J. Briquet ( Compt . 
Rend. Sc. Soc. Phys. et d'Hist. Natur. Geneva , 1920, 37, 15-19). A 
description of the leaves of a new species of Pertya (Compositae) found 
on the limestone mountains of Yunnan. These leaves are linear, stiff, 
cylindrical, and sessile ; they are about 5 mm. long and 1 mm. broad, 
and are protected when young by short, oval scales. The inner surface 
of the scales is velvety, while the outer surface is covered with long, 
straight, unicellular or multicellular hairs, with thick, very oblique cell- 
walls traversed by simple connecting passages ; these hairs form thick 
tufts from which the leaves emerge. The leaves are coiled so as to form 
a distinct inner chamber which communicates with the air by means of 
an elliptical slit. The external epidermis is formed of cells with excep- 
tionally thick outer walls, much reduced cavities, and internal walls of 
cellulose slightly thickened and penetrated by numerous canals; the 
external cuticle has a thick outer layer penetrated by canals, and an 
internal, cuticularized region through which the canals do not penetrate. 
The internal epidermis which lines the leaf-chamber is of normal type, 
with numerous small stomata, and covered with a fine cuticle ; there is 
no trace of the thickening found in the external epidermis. The 
chamber itself is lined with long thin hairs directed towards the base 
of the leaf ; the structure of these hairs resembles that of the scale- 
hairs. The mesophyll is normal, but has unusually large chloroplasts, 
and the vascular bundles are poorly developed. The author believes 
that the canals of the external epidermis are a device for facilitating 
the passage of food-material to this region during the time when, having 
emerged from the protective scales, the leaves require a rapidly-formed 
protective covering to defend them from the intense sunshine and dry- 
ness to which they are exposed. This is the first recorded instance of a 
xerophytic type of leaf in this genus. S. G. 
Physiology. 
Reserve Material in Pollen-grains. — Helen Bodmer ( Viertel - 
jahrsch. Naturfor. Gesellsch. Zurich , 1921, 66, 339-46). An account 
of investigations as to the nature of the food-reserves in anemophilous 
pollen, with special reference to Populus tremida and Fraxinus excelsior. 
It is found that the time of dehiscence does not always correspond with 
a similar stage in the formation of the food-reserve. In Fraxinus the 
transformation of starch into fat goes on equally well in the moist 
anther and in the dry air subsequent to dehiscence, and the pollen-grain 
germinates under suitable conditions of moisture without regard to the 
presence or absence of starch. The fat-reserve of the pollen of Luzula 
campestris and Juncus articulatus gives rise to a longer pollen-tube 
than does the starch-reserve of Plantago lanceolata and Rumex acetosa. 
Newly opened flowers of starved plants of Plantago lanceolata and of 
various species of Graminese shed pollen, at the end of the first day, in 
which the fat predominates in quantity over the starch ; the same kind 
of pollen is shed by Rumex scutatus, Carex montana and Schoenoplectus 
lacustris in two to three days. After a longer period of starvation the 
pollen shed is poor in food -reserves and has large vacuoles. In 
