Vol. XI. No. 261. 



THE AQRICDLTDRAL NEWS. 



141 



STUDENTS' CORNER. 



MAY. 



First Period. 

 Seasonal Notes. 



In the present quarter of the year, the work that was 

 indicated to be done in lime plantations for the last quarter 

 should be continued. This includes drainage, pruning, 

 weeding and mulching. Under what conditions are lime 

 cultivations most likely to exhibit a need for drainage, and 

 what are the signs that such conditions exist? In what cir- 

 cumstances do you consider that lime trees require pruning? 

 State what objections, if any, there are to the pruning of 

 limes, and what precautions should be employed in carrying 

 it out. 



Manure may be applied at the present time, and when 

 the period of regular rainfall begins. Among useful manures 

 for the purpose are sulphate of ammonia, nitrate of lime and 

 various proprietary manures. What are the essential differ- 

 ences between manures contained in the last mentioned 

 designation and those named first? It will be observed that 

 they all contain nitrogen. What change.? usually take place in 

 regard to this substance before it is absorbed by plants? With 

 reference to these changes, it must not be considered that 

 they are absolutely necessary with respect to many substances 

 that contain nitrogen, for recent work has proved that several 

 compounds carrying this element can be absorbed by plants 

 under conditions such that there could not be any trans- 

 formation into nitrates, with the aid of bacteria. 



Usually, the time for setting out young lime plants in 

 the field arrives in .June, and in .May the holes should be 

 prepared for the purpose of receiving them in the carefully 

 marked out positions that the plants will occupy. These 

 holes should lie about 2 feet deep, and 2 feet wide and long. 

 They are allowed to remain open for a few weeks before the 

 limes are planted in them. Why is this done? 



Give an account of the characteristics of a well grown 

 lime seedling, and supply the details of the treatment that 

 seedlings receive in the nursery in order that they may 

 acquire the desirable characteristics. 



The sowing of lime seeds at the present time is likely to 

 be successful in those islands possessing the larger rainfall, as 

 they are not liable to be killed by the disease known as 

 damping off — a disease that is most generally found to pre- 

 vail during wet weather. Give an account of the life history 

 of the fungus that produces this disease. 



The work that has been outlined for limes will include 

 the careful treatment of all wounds made in pruning or in 

 any other way. Wounds should be dressed with an antiseptic 

 substance or mixture which will discourage the attacks of 

 fungi and insects A useful mixture for the purpo.se may be 

 made from resin oil and tar. Observe the way in which the 

 wounds heal, both large and small, and make sketches of the 

 progress of the healing process. 



Lastly, in regard to limes, the present time is likely to 

 form a useful opportunity for the study of scale insect pests 

 of the plant, and of the fungi that are parasitic on them. 



Questions for Candidates. 

 Preliminary Questions. 



(1) Give a list of manures that are used specially for 

 providing phosphorus. 



(2) Write a description of whatjs seen in the case of 

 a scale insect attacked by a fungus parasite 



(3) Provide a list of the chief exports of the island in 

 which you live, in the order of their importance. 



Intermedi.\te Questions. 



(1) Write an account of the manufacture of any manure 

 that is used to supply phosphorus. 



(2) Give as many examples as you can of scale insects 

 that you have seen to be attacked by fungi. 



(3) Supply a description of the way in which any agri- 

 cultural product with which you are familiar is packed and 

 shipped. 



Final Questions. 



(1) What part does the element phosphorus occupy in 

 regard to the nutrition of plants? 



(2) AVrite an account of the natural and artificial 

 methods employed in practice for keeping scale insects in 

 check. 



(3) Give a general account of the conditions existing in 

 regard to the two chief crops of the island in which you live, 

 and state how far the replacement of the first in value, by the 

 second, is expedient. 



PLANTS AND RADIUM. 



Details of experiments that have been undertaken for the 

 purpose of ascertaining the effect of radium on plants, under 

 certain conditions, are given in the Comples Rendus de la 

 Sock'tii de Biolofjie, Paris, 1910, p. 523, and 1911, p. 419. 

 The accounts are abstracted in the Experiment Station Record, 

 Vol. XXV, p. 523, and the matter there given is used for pre- 

 senting the following facts. 



The unopened flower buds and the ovaries of Lilium 

 were exposed to radium rays of different strengths, with the 

 result that the former organs were arrested in their develop- 

 ment and commenced to dry up, while complete atrophy of the 

 ovaries and stigmas took place, and the anthers either did 

 not attain complete development or the period required for 

 them to come to maturity was much lengthened. 



Microscopical examination of the anthers and ovaries 

 showed that there were either no nuclei, or incompletely 

 developed nuclei, in the former; in the ovaries the embryo- 

 sacs were atrophied, and this was not the extent of the 

 damage, for the same circumstance had occurred in the entire 

 ovule. 



In further work, it was found that it was sufficient 

 merely to subject the flowers of Lilium to the action of the 

 rays to cause the underground stems (rhizomes) to rot or 

 fail to grow, so that it is concluded that the exposure of the 

 floral organs to strong radium rays has the result of causing 

 a general derangement of the vegetative part of the plant. 



Observations were al.«o made with Linuni catharticum, 

 a plant commonly known as purging flax, which was grown 

 from seed in soil containing radium salts. Under the 

 condition, a general retardation was caused in the germina- 

 tion of the seeds and the growth of the plant. A further 

 observation went to show that the number of leaves pro- 

 duced on plants of this kind was increased by exposure to 

 the radium rays. 



