Vol. V. No. 119. 



THE AGRICULTURAL NEWS. 



365 



SCIENCE NOTES. 



Germination Retarded by Seed-coats. 



In a valuable paper on the ' Role of Seed-coats in 

 delayed Germination,' in the Botunical Gazette for 

 October, ilr. W. Crocker has shown that delayed 

 germination is often due to the seed-coat rather than 

 to the embryos. 



A thin seed-coat, which lets in enough water, may keep 

 out air so well that the embryo cannot get enough to breathe, 

 and so cannot grow until the shell has decayed enough to 

 form a hole through which air can pass. 



Mr. Crocker records many experiments with the cockle 

 bur {Xanthium), which is covered with little hooks and 

 contains two seeds, an upper and a lower. In the upper seed 

 the delay (of two years) is secured by the seed-coat excluding 

 oxygen. 



If a seed were accidentally wounded in removing it 

 from the bur, it began to grow just where it was cut. If the 

 wound were at the upper end of the seed-leaves, away from 

 the radicle, the growth of the seedling was the reverse of that 

 u.sual with the plantlet in seeds, in which the radicle usually 

 grows out first. In this case the seed-leaves grew out first. 



On removing the delicate seed-coats from the seeds of 

 a cockle bur (X canadense), both upper and lower seeds 

 germinated equally and fully in nine days at about 68' F. 

 All other kinds of cockle bur experimented with gave similar 

 results. Hence it was the delicate seed-coat that caused the 

 upper seeds to wait so long before germinating. 



It was found that at 74° F. the lower seeds took up 

 about one and a half times as much oxygen, when the 

 seed-coats were removed, while the upper seeds took up 

 nearly two and a half times as much oxygen when the 

 seed-coats were taken off. And this difference between the 

 two kinds of seeds would be greater when the seed-coats were 

 thoroughly wetted, which was not the case in these experi- 

 ments. Hence the seed-coat of the upper seed was a much 

 greater hindrance to the passage of that part of the air which 

 is essential for breathing than the seed-coat of the lower 

 seed. Mr. Crocker also found by direct experiments on 

 a seed-coat, that oxygen passes through ip one and a half 

 times as fast at 81° F. as at 68° F. Hence the fact that 

 a higher temperature causes the upper seeds to germinate 

 quickly is explained. At the higher temperature the seeds 

 with the seed-coats on absorbed proportionately less oxygen 

 which they did not give out as carbon dioxide. 



From all these carefully worked out experiments a full 

 understanding of the delay of the upper seed in germination 

 can be reached. Enough oxygen gets through the seed-coat 

 of the lower seeds to start them germinating. The part of 

 the bur covering the upper seed does not easily decay, and so 

 the seed-coat of the upper seed lasts usually for two years, 

 and sometimes for three or four years, and until this seed- 

 coat is broken through by rotting, the upper seeds will not 

 germinate. The experiments proved conclusively that the 

 cause of the retarded germination lies not in the embryo but 

 in the seed-coat. 



IMr. Crocker extended his work to many other seeds. 

 It tends to explain the appearance of quite strange plants and 

 Mowers on a patch of forest cleared by fire, a fact noticeable 

 in the forests of England and the United States. It would 

 be interesting to know if any strange plants appear on the 

 .spots in West Indian forests where charcoal burners have 

 been at work. 



Distribution of Winged Seeds. 



It is well known that many seeds are provided with 

 wings for the purpose of securing their distribution by the 

 wind. The mahogany affords a good example of such winged 

 seeds. An examination of these shows that there are 

 often provisions for securing that the seeds shall be blown as 

 far as possible from the parent tree. ; ■ 



It may not have been noticed that the mahogany seed, 

 as it descends from the opened capsule, rotates rapidly. It 

 thus forms what may be termed a ' vegetable aeroplane,' the 

 rotation evidently serving to retard to a considerable extent 

 the rapidity of its descent. On examination the wing is 

 seen to be curved like the blade of a screw propeller. The 

 retardation is the same as that which would be experienced 

 if a .sailing ship, with auxiliary steam power, were to use her 

 sails alone, without unshipping or feathering her screw. In 

 a wind this vegetable gliding plane would be blown further 

 from the tree, when a gust had dislodged it from the capsule, 

 than if it merely had a fiat wing. 



Another tree, Trrplaris, to be seen in some of the AVest 

 Indian Botanic Stations, has three bent wings, forming 

 a more perfect screw propeller to keep it Hying in the air 

 as long as possible. 



DEPARTMENT NEWS. 



The Imperial Commissioner of Agriculture returned 

 from Canada and landed at Barbados on Friday 

 morning, November 9. The following are the dates 

 of his tour in the Northern Islands: Nevis, October 

 14 to 18; St. Kitt's, October 19 to 24: Antigua, 

 October 2.5 to 27 ; Dominica, October 28 to 31 ; 

 Montserrat, November I to 3 ; St. Lucia, November 

 4 to 7 ; St. Vincent, November 8. In addition to the 

 official inspection of the Botanic and Kxperitiient 

 Stations and of the Agricultural Schools at Dominica 

 and St. Lucia, public meetings were addressed at 

 Nevis, So. Kitt's, Antigua, Dominica, Montserrat, and 

 St. Lucia, and conferences with members of the 

 Agricultural Experiments Committees took place at 

 Dominica and St. Lucia. 



The Hon. Dr. Francis Watts, C.M.G., Government 

 Analytical and Agricultural Chemist and Superin- 

 tendent of Agriculture for the Leeward Islands, who 

 is on vacation leave of absence, is expected to embark 

 for the West Indies at Southampton in R. M. S. 

 ' Orinoco ' on November 21, which is due at Barbados 

 on December 4 nest. 



Mr. H. A. Ballon, M.Sc, Entomologist on the 



staff of the Imperial Department of Agriculture, left 

 -Barbados for St. Lucia in the S. S. 'Orinoco' on 

 November 10, for the purpose of investigating insect 

 pests of cacao in that island. 



Mr. Thomas Thornton, A.R.C.S., Travelling 

 Inspector in connexion with Cotton Investigations, 

 returned to Barbados from the Northern Islands in 

 R. M. S. ' Eden ' on Monday, November 5. Mr. Thornton 

 left for St. Vincent on November 6, to assist with 

 experiments in seed selection of cotton. 



