No. 387.] PLANT MORPHOLOGY AND PHYSIOLOGY. 201 
internal anatomy and its development are treated in full. This is 
intended by the author as the first of a series of life histories of 
important species of this family which are expected to yield data for 
a better understanding of principles of morphological modification 
under the influence of changing ecological factors. 
This plant, which lives under arid conditions, represents the extreme 
of specialization along the Echinocactus line, as is clearly indicated 
by its embryology. It has a highly differentiated anatomy, the tra- 
cheid system being better developed than in any other plant known 
to the author. The mamillz show three concentric rings of vascular 
bundles, a cortical ring, a ring leading to the spine system, and a 
central ring going to the flowers. 
Pror. Byron D. HALSTED: Root Tubercules upon Spring and 
Autumn Grown Legumes. — The ninth successive crop of wax beans 
upon the same plot (one-twentieth acre) grown in the spring of 1898 
consisted of plants, the roots of which bore numerous large, nearly 
spherical tubercles. The plants of the succeeding crop grown in the 
summer upon the same soil had very few of the root galls. 
The cause of this remarkable difference in the behavior of the 
same variety of leguminous plant in the same germ-laden soil must 
be ascribed to changes in soil conditions. During the early growth 
of the spring plants the soil was considerably cooler than in August, 
when the second crop was passing through the initial stages of devel- 
opment. There was, doubtless, aside from the different temperature 
of the soil, a wide difference in the amount of available soil nitrogen, 
it being much less in the comparatively cool earth of May than in the 
warmer ground of August. 
The nitrifying germs of the soil, being more active in midsummer, 
provided a daily supply of combined nitrogen for the young growing 
plants. On the other hand, the spring crop, not having this ample 
supply was “nitrogen-hungry,” and this furnished the proper condi- 
tion upon the part of the host plant for the abundant development 
of the tubercles. 
Successful inoculation of the plants with soil-extract or the pure 
culture of the tubercle germ “ Nitragin ” is dependent largely upon 
soil conditions, and many widely varying results may here find an 
explanation. 
Francis E. Lioyp: Further Notes on the Comparative Embryology 
of the Rubiacee.—The genera studied include Houstonia, Rubia, 
Sherardia, Vaillantia, Crucianella, Galium, and Asperula. 
