97° 
pollen-tube is formed, which penetrates the ovule, but does not 
come in contact with thearchegonium. The nucleus of the pollen- 
tube divides, parallel to the long axis of the tube, into two daughter 
nuclei, one of which continues to grow and divides again into twoin 
asimilar way. The latter two daughter-cells become the ciliated mo- 
tile male gametes. These spermatozoids are described as exhibiting 
a nucleus completely surrounded by cytoplasm, They are of an 
ovoid form, 82 long by 49 » broad; the head consists of three 
spiral turns, these bearing numerous cilia, and a pointed tail is also 
present. As soon as the spermatozoids escape from the pollen- 
tube into a fluid which by this time has accumulated in the nucleus, 
they swim quite actively about with whirling movements. 
The writer does not state that he has traced out the course of 
events from this time on. Prof. Ikeno has found in Cycas revoluta 
Spermatozoids similar in structure and development to those of — 
Ginko, but has not seen them in motion, as his observations were 
confined to material collected at a distance and treated with various 
fixing reagents. MarsHa.Lyt A. Howe. 
Contributions towards a Monograph of the Laboulbeniaceae. By 
Roland Thaxter. Memoirs Am. Acad, 12: 187-429. pl. 1-26. 
D. 1896. 
This is one of the most elaborate works that has yet appeared 
on American mycology and has set a pace that it will be diffi- 
cult for many to follow. The author has been peculiarly for- 
tunate in having before him an almost open field, since, of the 158 
Species known, 130 are American and with one or two exceptions 
have been described by the author himself; he has, moreover, de- 
Scribed several of the exotic species. It isa privilege that few 
can enjoy to enter a field so free from the necessity, to borrow an 
€xpression from a colleague, “ of first clearing the Augean stable 
of synonymy.” The limits of species and genera have thus been 
a new problem and the group is fortunate in thus having its out- 
lines marked by a skilled investigator. Besides the careful diag- 
noses of genera and species, there are twenty-six plates that are as 
nearly perfect as the art both of the author and of the engraver 
can make them; these illustrate all the species described. The 
author also gives some general discussion of the group and brings 
Out more fully than in his former papers the two most important — 
