AGRICULTURAL ROTANV. 923 



"Variation in the sexuality of plants, 1 >. I'.ois ( A'f r. llorl. \l'iuix\. 7.V 

 [I'.iii^i). \<i. 7, II. lo.i). — Attention is oallt'd to liii,' variations i-ci)orte(l in st'xu- 

 alii.v of ilowers of species of willow and I'istacia terehiiithus. 



In tlic cnsf^ of tlio willow it is clainiod that tli(> flowers woro nioiv or less 

 i'(':_'iilarly iici'iiKiphroiiil ir willi a \ar.\inLC pr('|)oii(l('r;inc(' of male or female 

 ilowers, depending upt)n the water supply of the ])laiits. Suhnierj^enee of wil- 

 lows hy the overtlowiiij; of rivers was found to markedly affect the character 

 of the flowers. When suhmerf^ed deeply and for a long time, most of the 

 Ilowers noticed were male, while on plants of the some species that were only 

 temporarily inundated female flowers predominated. 



The observations on Pistacia were made of cuttings from the same plant, 

 one ^rowin^^ in a dry situation, while the other was irrigated. The irrigated 

 plant bore male, female, and hermaphroditic flowers in the same clustei's, 

 while the one in dry soil bore only unisexual flowers. The following year the 

 water in the irrigation canal failed and the inflorescences of the plant growing 

 on its banks contained only unisexual flowers. 



The g^'owth of plants and the absoi-ption of mineral substances, R. 

 Chodat, A. MoNiViER, and Dki.kaxo (Bill, llvrh. Bols.sicr, 2. .scr., 7 {1901), Ao. Ji, 

 pp. S'>()-3').l). — The authors state that the growth of jdauts and each of the 

 [irincipal mineral substances taken up by them may be represented by a cnrve 

 ui) to the maximum, after which there is not only less assimilation hut a return 

 to the soil of mineral substances actually takes place. 



A series of experiments was carried on not only to demonstrate the law of 

 absorption of mineral substances, but also to test the value of different nitrog- 

 enous materials for the growth of oats. The oats were seeded in plats on 

 April 12 and received identical treatment, except as to the form of nitrogen. 

 Tlie forms of nitrogen given were nitrate of soda, nitrite of soda, sulphate of 

 annnonia, and calcium cyananud. One hundred plants were taken from each 

 plat and analyzed at intervals of about a week from the beginning to the end 

 of growth, a period of 74 days elapsing between the first and last analyses. 



There was a constant acceleration in growth and absorption of mineral sub- 

 stances mt to the forty-third day, when the plants were in full flower. From 

 that date until the fiftieth day the increase took place more slowly, and after 

 50 days, when the grain was fully formed, there was a diminution not only in 

 assimilation but also in the total dry weight, the ash, and all the mineral sub- 

 stances contained in the ash. 



In the second part of the experiment it was found that intrate of soda gave 

 the highest yields not only of grain but also of straw, followed by sulphate of 

 annnonia. calcium cyanannd, and nitrite of soda. 



On the application of the theory of limiting factors to measurements 

 and observations of growth in Ceylon, A. M. Smith {Ann. Roy. Hot. Gard. 

 I'cntihiiiint. .] {l!K)(i), Xo. 2, pp. 303-375, plti. .'/). — Investigations were con- 

 (luiled with a lunnber of tropical species of plants to test the theory of Black- 

 man, which is essentially as follows: As a rule, a single one of the physical 

 factors limiting the physiological processes of' plants determines the rapidity 

 of the process, and when the rapidity of the physiological process is determined 

 l)y a number of factors the slowest acting will limit the rate of growth. 



The author has studied temperature, water supply, light, atmospheric pres- 

 sure, wind velocity, etc.. as factors limiting growth, and he divides his results 

 according to whether or not the plants experiniente(l ujKm possessed a reserve 

 sujiply of food material. It was found that for plants having an abundant 

 reserve food su])ply the three factors that limit the physiological processes are 



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