22 Brannon. — The Structure and Development of 



in the frail walls of these old exhausted cells, would almost 

 certainly have given preparations showing the empty cells 

 connected by wide openings, thus leading to the conclusion 

 that cell-fusion between these auxiliary cells had taken place. 



During much of the time devoted to the initial study of 

 Grinnellia, many attempts were made to carry it through 

 paraffine for the purpose of sectioning, but none were success- 

 ful. It was found on examination from time to time, as the 

 plants were being prepared for imbedding, that they endured 

 the action of absolute alcohol and the oils very well ; but in 

 every case the tissue was found to be too delicate to endure 

 the temperature necessary in the final process of imbedding, 

 even when the softest paraffine, melting at the low temperature 

 of 45° C, was employed. 



After repeated failures with paraffine the celloidin method 

 was tried. This proved somewhat more satisfactory, though 

 the prolonged treatment of sections with the oils used in 

 dissolving celloidin shrivelled and distorted them to such 

 an extent as to render observations partial and uncertain in 

 their results. Finally, having secured an abundance of 

 favourable material, and adopting the freezing methods and 

 apparatus perfected by Mr. W. J. V. Osterhout of Brown 

 University, the successful study of the cystocarpic develop- 

 ment of Grinnellia was undertaken, and very gratifying 

 results obtained. 



The great advantages of the freezing method in work on 

 Grinnellia are appreciated in the ability to make rapid 

 preparation of fresh tissue and to secure a great number 

 of sections with comparatively little labour. This latter 

 advantage makes the process especially valuable in showing 

 the relation of the evanescent trichogyne to the procarp. It 

 is difficult to observe this relationship by other methods, 

 since many of the cystocarps may be too young or too old 

 by a few days to show clearly the early stages of procarpic 

 development. 



A brief summary of this method may be given as follows : — 



A portion of the fresh frond is arranged in several layers, 



