THE DEVELOPMENT OF ANTHER, ETC. 203 



X ^ ^^ 



The same method may be used ?6T the prflTen of other plants, 



e.g. Orchids, species of Tulipa, Fritillaria, Nymphcea, &c. It will 

 be found that the time of appearance of the pollen-tube will vary 

 in different cases ; also that to obtain good results solutions of 

 sugar of different strengths will have to be used. In most cases a 

 solution of 10 per cent, or less will be found suitable. 



Development of Anther and Pollen. 



If transverse sections be made from very young buds of 

 Caltha, and successively from older ones up to the mature 

 flower, the development of the anther and of the pollen may be 

 traced. 



The material should be preserved in absolute alcohol (or strong 

 methylated spirit), and the sections should be treated with half 

 glycerine, half alcohol : this should be left exposed to the air in a 

 watch-glass, so that the alcohol may evaporate : mount in pure 

 glycerine. Anhydrous staining reagents may be employed, but 

 are not actually necessary. 



By following this method, sections may be prepared illustrat- 

 ing the division of hypodermal cells by periclinal walls of four 

 points in the young anther, corresponding in position to the four 

 pollen-sacs of the mature one : the outer layer thus produced is 

 the primary tapetal layer : the inner is the archesporimn : 

 tracing the development further, as it may be seen in older anthers, 

 verify the following points : 



i. The cells of the outer, or primary tapetal layer, undergo 

 division by successive periclinal walls into three, and the layers 

 thus produced develop respectively into 



a. The fibrous layer. 



b. The transitory layer directly within the fibrous cells. 



c. The tapetum, 



ii. The cells of the inner layer go to form the pollen-mother- 

 cells. 



The above points may be ascertained from a comparison of 

 sections of the very youngest anthers with those cut from older 

 ones. 



