246 BOTANICAL GAZETTE. 



and come from threads which grew from the spores. These sacs con- 

 tain one-celled spores, which when sown on the red cedar produce 

 the original form. This is one of the simplest kinds of rusts. Its 

 different forms were shown by magnified and colored diagrams, and 

 an incidental view was given of sacs on the upper side of the leaves. 

 It will be seen from this that in studying rusts on forest trees we 

 must study two kinds of trees. 



Rusts produce distortions of the stems of trees. One species, 

 which grows out into oraiige-colored points, causes a slight swelling 

 the first year, after which the points drop off, the mycelium remain- 

 ing behind. The tree tries to grow around the swelling, but the 

 spawn grows through the wood, and the tree again attempts to grow 

 around it. The result, in a few years, is a swelling which remains 

 after the fungus dies. Another fungus, which looks like a brownish 

 mass, and swells up when moistened, produces so large a knot as to 

 cut off the nourishment from the branch above, which consequently 

 dies, and is blown off by the wind. Such branches are called by the 

 Germans lie.cenbescti, or witches' brooms." 



Comparative Anatomy of Leaves. — Tlie writer was very much in- 

 terested last summer, while attending Prof. Goodale's summer school, 

 in a study of the various distribution of fibro-vascular bundles in 

 stems, in roots, in petioles, in the leaves of Conifersc^ etc. For the 

 purpose of suggesting a line of investigation to such as have like 

 tastes and suitable instruments, the following review, by Dr. Gray, 

 of a late memoir of Casimir DeCandolle. is copied from the Amer. 

 Jour, of Science and Arts. 



"One of Casimir DeCandolle's earliest studies was into the struc- 

 ture and relations of the fibro-vascular elements of the leaf, and the 

 results and deductions were brought out in his brief article entitled 

 Theorie de la Feuille, in the year 1858. The present paper is in no 

 respect theoretical, nor does it investigate the minute anatomy and 

 formation of the vascular bundles. But it presents a comparative 

 view of the general structure of the woody system of the petiole and 

 principal veins in a very considerable number of Dicotyledons, main- 

 ly trees, and belonging to different natural orders. In this way the 

 nature of the principal differences from species to species, and from 

 one order to another, are brought to view, and the taxonomical value 

 of such characters indicated. It is found that different species of the 

 genus sometimes accord, but sometimes difier notably in this part of 

 their anatomy. Wherefore the classificatory importance of these dif- 



