30 EXPERIMENT STATION RECORD. 



tained by the use of the isolated bacteria alone but especially when these were 

 combined with the nitragin cultures. 



The duration of the vitality of seeds of Orobanche crenata, N. Passerini 

 (Atti R. Accad. Econ. Agr. Geogr. Firenze, 5. ser., 7 {1910), No. 1, pp. 1-7). — 

 Experiments are reported in which the germination of seeds of 0. crenata was 

 tested in pots, the study being continued for 14 years. As a result the author 

 found that the seed lost practically all germinative ability after lying in the 

 soil for 8 years. 



The anatomy of some tubers, T. Reed (Ann. Bot. [London], 2-^ (1910), No. 

 95, pp. 537-5 JfS, pis. 2, dgms. 4 ) .—Attention is called to the fact that but little 

 investigation has been carried on on the anatomy of tubers, and the author 

 gives an account of studies made on the tubers of the potato and the artichoke. 



The tubers of the potato are said to arise as terminal swellings on long 

 underground stems or stolons, which arise in the axils of the lower leaves of 

 the main shoot and grow more or less horizontally outward, swelling sooner or 

 later at the tips to form tybers. The artichoke tubers arise as swellings on 

 the underground stems or stolons, which spring from the axils of scale leaves 

 at the base of the main shoot. The stolon may swell up at once and become a 

 tuber, or it may greatly elongate and give rise to a number of lateral tubers, 

 finally terminating itself in a tuber. 



The principal difference i» development between the two is that the potato 

 tubers are never formed laterally, as in the case of the artichoke. In structure 

 the potato tuber is formed mainly from medullary parenchyma and from the 

 parenchyma between the sylem and the medullary phloem. The latter source 

 is largely responsible for the scattered distribution of the medullary phloem 

 strands in the tuber. The medullary phloem probably serves as the channel for 

 carrying food material to the parenchymatous portion of the tuber, which is 

 covered by a layer of cork developed from the hypoderma. The tuber of the 

 artichoke differs from that of the potato in that it is made up of medullary 

 parenchyma, xylem, and medullary ray parenchyma. In neither of the tubers 

 is there much, if any, secondary lignification of elements. 



Experimental researches on vegetable assimilation and respiration, VI, 

 D. Thoday (Proc. Roy. Soc. [Londoni, Ser. B, 82 (1910), No. B 557, irp. Jf21-^50, 

 figs. 3). — An account is given of studies on assimilation in the open air, the 

 method used that employed by Sachs in which the dry weight of half the leaf 

 was used, but so modified as to make it more accurate. The material experi- 

 mented upon w;is sunflower and catalpa leaves. 



It was found that in the open air high rates of assimilation occur, although 

 there is but a small concentration of carbon dioxid in the atmosphere. In the 

 experiments with the sunflower, which agreed vei*y closely among themselves, 

 leaves which remained turgid, and so kept their stoma ta widely open, showed 

 an average net increase of nearly 17 mg. per hour in their dry weight per square 

 decimeter. If a moderate allowance is made for the assimilation of the car- 

 bon dioxid produced in respiration, the photosynthetic products reach a total 

 of about 18 mg. per hour. The rate of production is not uniform, at times 

 exceeding the average. 



The limiting factor of assimilation is the internal leaf temperature when 

 the stomata are open enough to allow carbon dioxid assimilation, providing the 

 temperature does not exceed 23 to 25° C. When the sunflower leaves lost their 

 turgidity the rate of assimilation was considerably diminished. 



Compared with the sunflower, the catalpa assimilated at a much lower rate, 

 a fact which is correlated with the absence of stomata from the upper surface 

 of the leaves. Under the conditions which enabled the sunflower leaves to 



