TRANSACTIONS OF SECTION K. 861 



In S. Ludwigii the nucleus appears to possess the normal structure of a nucleus 

 a nuclear membrane being present, together with a nuclear network and a nucleolus. 

 The nucleolus appears to contain all the chromatin substance, and in the process 

 of division increases in size and divides into two, each portion becoming a new 

 nucleus. 



In S. Pastorianus the nucleus is similar in structure to that of S. Ludwigiif 

 except that a distinct nuclear network could not be seen. The process of division 

 is likewise bimilar to that observed in S. Ludivigii. 



The process of spore-formation was observed in S. cerevisem. In a cell about 

 to sporulate the large vacuole or vacuoles disappear, and the protoplasm becomes 

 filled with a large number of very small ones, so that its texture appears spongy. 

 At this stage the nucleus is found in the centre of the cell, and appears to be 

 homogeneous in structure. Soon, however, deeply stained granules appear in it, 

 and these accumulate in the centre, forming a spherical mass, which looks exactly 

 like a nucleolus. When this nucleus divides its outline becomes irregular, and 

 the granules arrange themselves in the form of a short rod surrounded by the othe? 

 portion of the nucleus, which stains differently and appears to form a structure of 

 the nature of a spindle. The granules separate into two groups, and each group 

 becomes a nucleus. The two nuclei thus formed again divide, and four nuclei are 

 produced, each of which becomes the nucleus of a spore. A small quantity of 

 protoplasm accumulates round each nucleus, spore membranes appear, and four 

 spores are thus formed, standing in the remainder of the protoplasm, from which 

 ultimately the thick spore membranes are produced. 



We may, I think, regard the process of nuclear division in spore-formation as a 

 simple form of karyokinesis. 



6. A Disease of Tomatoes. By W. G. P. Ellis, M.A., Cambridge. 



From diseased tomatoes received in August 1896 from Jersey the associated 

 fungi and hacteria were isolated and cultivated on nutrient gelatine, and the 

 mycelium was traced in sections of the fruits. On removing the first skin with 

 carefully sterilised instruments the mycelium within the fruit formed in a short 

 time the well-known sporangiophores of Mucor stolonifer. Though late in the 

 season (August 31, 1896), infection of sound plants at the University Botanic 

 Gardens, Cambridge, from pure cultures caused a disease resembling that of the 

 fruits received in August and September from the grower. Experiments are now 

 (July 1897) in progress to determine (1) whether the fungi, ohtained, other than 

 Mucor stolonifer, cause disease, and (2) the site of infection. 



7. On the Chimney-shaped Stomata q/" Holaoantha Emoryi. 

 By Professor Charles E. Bessey. 



This prickly, leafless shrub, called the ' Burro Thorn,' ' Sacred Thorn,' ' Cruci- 

 fixion Thorn,' ' Corono de Christo,' &c., is a native of the arid regions of Southern 

 Arizona, where it was discovered fifty years ago by Major Emory, of the United 

 States Army. It is supplied with remarkable breathing pores, which are evidently 

 designed to enable the plant to obtain carbon dioxide, while at the same time pre- 

 venting the loss of water from its interior moist tissues. The epidermis is of 

 extraordinary thickness, and the stomata have long, narrow, chimney-shaped 

 openings above them, terminating in hollow papillae, which project some distance 

 above the surface. 



8. Some Considerations upon the Functions of Stomata, 

 By Professor Charles E. Bessey. 



The author summarily reviewed the structure of stomata and discussed the 

 needs of aquatic, terrestrial, and aerial plants as to their getting of food, and the 



