





a he li aie 

1901] CURRENT LITERATURE 209 
ai pe Interesting hypotheses are given on the origin of the Austral 
form WLES 
LLE. RODRIGUE® has made a painstaking study of the anatomy of 
variegated leaves with a view to ascertaining the relation between color and 
structure. The author gives an excellent summary of the literature of her 
subject, and makes a detailed study of thirty-three species. The white effect 
is due in most cases to the absence of chlorophyll, although a similar appear- 
ance is given by certain dissolved pigments, and by the reflection of light in 
some special instances. The modifications in the latter cases are slight and 
are confined to the epidermis, Where chlorophyll is absent, the leaf may be 
regarded as diseased, and the tissues are different from normal leaves, having 
no palisade development, and consequently a great reduction in thickness, 
In other words, the hile tissues remain pitta where chlorophyll is 
absent.—H. C. Cov 
ALB, NILSSON? has made some interesting studies on the dynamics of 
some Swedish plant societies, especially of cliffs and moors. He finds three 
types of cliffs, those which are forested either with conifers or deciduous 
trees, and those without trees. On all cliffs the first plants are crustaceous 
lichens. On the conifer cliffs there follow in succession fruticose lichens, 
herbs, heath plants, conifers. Cliffs with deciduous trees have no fruticose 
lichen or heath stages, the author attributing the absence of the fruticose 
lichens to wind. On the third type of cliff the lichens remain longer and 
foliose lichens and mosses are added to the stages after crustaceous lichens. 
Dying lakes pass into sedge moors, then into cotton-grass moors, finally into 
shrub moors and forest moors with pines or birches. Retrogressive phases 
are common on the moors, lichens growing over the peat moss and shrubs; 
again the water collects and the lichens pass away. The peat moss appears 
again and we have what Nilsson calls a secondary moor.—H. C. COWLES. 
THE STYLIDIACEAE (Candolleaceae in Engler and Prantl’s Nat. Pflanzen- 
Jam), a small family almost confined to Australia, New Zealand, and farther 
India, has been recently studied by G. P. Burns. The greater part of the 
paper is devoted to a morphological study of the various tissues. Before 
fertilization the structures of the embryo sac present no unusual features, . 
but immediately after the entrance of the pollen tube the micropylar portion 
of the sac grows out into an enormous haustorium much larger than the 
remainder of the sac. The endosperm forms rapidly and fills the sac with 
tissue before the first division of the egg takes place. Shortly after fertili- 
zation the antipodals disintegrate, and the posterior portion of the sac also 
8 Mém. l’Herb, Boiss. 17: 1900. 9 Bot. Not. 1899: 89-101; 123-135. 
* Beitrage zur Kentniss der Stylidiaceen. Flora 87: 313-354- pls. 13, 14 (and 45 
text figures). 1900. 
