t914] CURRENT LITERATURE 245 
pollen had ever reached the stigma, or that having reached it, favorable con- 
ditions for germination were present. Laburnum vulgare, as a case in point, 
* remains self-sterile in the absence of slight mutilations produced by insect 
visitors. Many examples of species with both self-sterile and self-fertile races 
or varieties are mentioned. An enormous variation in the degree of self- 
sterility is noted: at one extreme, self-pollination produces but slightly fewer 
seeds than cross-pollination; while at the other, a few cases are known in which 
the stigma and pollen of the same flower are mutually poisonous. Environ- 
ment produces a marked effect on this phenomenon, as often a change in 
climate changes self-sterile plants to self-fertile ones. Biophytum sensitivum is 
recorded as self-sterile in its open and self-fertile in its cleistogamous flowers. 
owledge of causes is exceedingly vague and fragmentary. Examination 
of stigmas fertilized with their own pollen has shown that although germination 
‘takes place, the pollen tube is inhibited in its growth in some way so that it 
never reaches the embryo sac. In Jost’s experiments no artificial medium was 
discovered in which pollen tubes would grow their normal length. ComPTON 
Suggests the presence of a soluble diffusible substance in the stigmatic or stylar 
ssues which acts in a positive manner toward promoting pollen tube growth. 
An analogy between self-fertility and immunity, and self-fertility and infection 
is drawn, in line with the suggestive work of Jost, Scutrr-GroRGIONI, and 
others. A special section is devoted to a review of the investigations of BAurR, 
Correns, and Compton, on the inheritance of self-sterility, and its racial as 
°pposed to its individual nature. Suggestive analogies are also drawn between 
self-sterility and certain sexual phenomena, such as non-conjugation and 
The wood of Pinus.—Groom and Rusxron;? in their detailed account of 
the wood of the five East Indian pines, have kept several objects in view: the 
affinities of the species, tropical (hydrophytic) or xerophytic features of the 
Wood structure, relationship of the latter to leaf structure, and the nature of 
the so-called “ Sanio.” They have devoted the first part of their work 
e # general statement and discussion, and in the second part have given a 
etailed escription of each species. : 
_ P. excelsa and P. Gerardiana belong to the HapLoxyLon section, having 
Single bundles to the leaves, deciduous sheaths on the spurs, tangential pitting 
Cir 
of ae Groom, PERcy, and Rusuton, W., Structure of the wood of East Indian species 
ab i - Jour. Linn. Soc. Bot. 41:457-490. pls. 24,25. 1913. GROOM has also given 
aoa account of the critical identification of the wood of the five East Indian pines in 
n Forester 39:409-411. 1913. 
