ARTIFICIAL GERMINATION OF POLLEN. 393 



Lysimachia nummularia (Creeping Jenny), Agapanthus, Lobelia, 

 Liliwn, Aquilegia. Many pollen-grains lose their capacity for 

 germination if the water contains small quantities of mineral salts, 

 since these are poisonous to them. Sometimes transverse walls 

 are formed in the pollen-tube, as, e.g., in Montbretia (Tritonia), 

 cultivated in 7 per cent, sugar and 1J per cent, gelatine. Sepa- 

 rate protoplasmic movements may then take place in each cell. 

 The growth of the pollen-tube in this case also is exceedingly 

 rapid, the elongation being visible with such a low magnifying 

 power as 200 diameters. 



