ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
743 
Glaucosity of Leaves.* * * § — According to Prof. F. Delpino, when the 
formation of wax in the outermost walls of epidermal cells is sufficiently 
great for it to be exuded in the form of rodlets, it serves the purpose 
not merely of reducing transpiration and confining this function to the 
stomates, but has also a protective function in preventing ants and other 
insects from crawling over them and reaching the organs which they 
would otherwise injure. 
Aerial Roots of Dicotyledons. f — Herr L. Keller has examined the 
structure of the aerial roots of seventeen species of terrestrial plants 
belonging to the natural orders Asclepiadeae, Gesneracese, Bignoniacese, 
Begoniaceas, Marcgraviacese, Vitacete, Urticacese, Piperaceas, Opuntiaceae, 
and Rosaceae ; he finds that they present no analogy to the aerial roots 
of Monocotyledons. They have no velamen, and the endoderm is not 
composed of long and short cells. In all important points of structure 
the aerial correspond to the underground roots of the same species ; 
the differences consist chiefly in the presence in the cortex of scleren- 
chymatous cells or of crystals, or in details connected with the environ- 
ment of the organ. Various special points of structure characteristic 
of the individual species are described in detail. 
Splitting of Roots and Rhizomes.J — Herr L. Jost discusses the 
phenomena connected with the splitting off of the active and living from 
the dead tissue, which occurs in the course of their secondary growth in 
thickness in some roots and rhizomes ; those specially examined were 
Gentiana cruciata, Corydalis nobilis , G. ochroleuca , Aconitum Lycoctonum, 
Salvia pratensis, and Sedum Aizoon. He finds it to depend on the dying 
of those portions of tissue which are in direct connection with the 
new annual organs, the leaves and flower-stalks. The living parts may 
be cut off from these dead portions by a periderm composed of several 
layers, or may be surrounded by a single or by a few layers of cork- 
cell, or there may even be no suberized membrane. 
Structure of Sarcodes.§ — Prof. F. W. Oliver describes in detail the 
structure of this little-known genus from California belonging to the 
MonotropeaB. S. sanguinea is a saprophyte growing among roots of 
pine-trees, but without any organic attachment to them by means of 
haustoria ; its roots are closely enveloped by a mycorhiza, which, 
differently from what is the case in Monotropa , clothes them up to the 
tips. It is entirely destitute of chlorophyll, but the whole of the aerial 
portion of the plant is coloured a brilliant crimson, due to the presence 
in the superficial cells of a soluble red pigment probably allied to tannin. 
The starch-grains which abundantly fill the parenchyme are undis- 
tinguishable, in physical and chemical properties, from those of ordinary 
green plants. The leaves are reduced to scaly imbricate structures, and 
stomates are entirely wanting. The filaments of the fungus-mycele 
never enter the epidermal cells. The lateral roots in Sarcodes have an 
exogenous origin, and differ in this respect from those of Monotropa. 
* Malpighia, iv. (1890) pp. 17-20. 
f ‘ Anat. Studien lib. d. Luftwurzeln einiger Dikotyledonen,’ Heidelber^ 1889 
44 pp. and 1 pi. See Bot. Centralbl., xliii. (1890) p. 149. 
t Bot. Ztg., xlviii. (1890) pp. 433-45, 453-62, 469-80, 485-93, 501-10 (1 pi ) 
§ Ann. of Bot., iv. (1890) pp. 303-26 (5 pis.). 
