PRIZE QUESTIONS OF SCIENTIFIC SOCIETIES. 449 



manner in which other countries construct locks of extraordinary di- 

 mension; and which of those modes of construction deserves prefer- 

 ence? Or, are there other modes of construction imaginable and 

 practicable for the construction of similar locks in this country?" 



9. Question 120. As the most recent observations of Dr. H. Schacht 

 upon the origin of the lacteal vessels of the CJarica papaya* con- 

 firmed his previous experiments, published in the Botanic Journal 

 of Von Mohl and Schlechtendal in 1851, as well as in his treatise on 

 the Anatomy and Physiology of Vegetables, and, as they contradict 

 the well-known observations of an anonymous writer in the same Bo- 

 tanic Journal in 18-4G, this society desires new observations with a 

 view to putting an end, if possible, to all doubts that still exist as to 

 the origin of the organs in question. The society, therefore, pro- 

 poses the following question : "How do the lacteal vessels originate 

 in the vegetable kingdom ? In the intercellular canals of the cells, 

 or in what other manner ? And are those organs, as Dr. Schacht 

 maintains, identical with ramified cortical fibres?" 



The society requires the observations to be extended over different 

 natural families of the vegetable kingdom; that they be illustrated by 

 drawings, and, if possible, by microscopic preparations. 



10. Question 121. During the last few years many plants have been 

 attacked by various diseases to such an extent that the crops have 

 been deficient, or a total failure, and that the plants themselves have 

 languished and died. 



This phenomenon deserves the attention of naturalists and of rural 

 economists, alike with reference to science and to practice. 



It is not to be wondered at, therefore, that this subject has occu- 

 pied the attention of many naturalists. But as hitherto their essays 

 have not produced any satisfactory results, as their views and expla- 

 nations are constantly contradictory, and finally, as the number of 

 the species and varieties of plants which suffer from disease seems to 

 increase, the necessity for such researches is the more obvious and 

 urgent. 



This society, therefore, asks the following question : 



"Will scientific men make an anatomico-physiological examination 

 of the diseases of one of the most important of the cultivated plants, 

 accompanied by a critical review of the principal theories concerning 

 the diseases, and also by an indication of the means of preventing 

 or counteracting them ? " 



The society desires at the same time that, as far as possible, mi- 

 croscopic preparations and drawings be made to illustrate the results 

 of the examination. 



11. Question 122. Have some portions of the sun's surface a higher 

 degree of temperature than others; and if so, do the same portions 

 always possess that higher temperature ? 



12. Question 123. "Light, heat, electricity, and magnetism, those 

 manifestations of force which formerly were attributed to imponder- 



^' AnnaUs des Sciences Naturelks, 4th series, vol. 8, page 164-. 



29 



