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The development of the embryo-sac and embryo of Potamogeton 



ucens 



Melville Thurston Cook 

 (with plates 9 and 10 ) 



The purpose of this study was to compare the development of 

 the embryo-sac and embryo of this plant with those of other well- 

 recognized monocotyledonous plants and with the Nymphaeaceae ; 

 also for the purpose of comparison with Holferty's (9) paper on 

 Potamogeton natans and Wiegand's (14) paper on RJoliosus. This 

 became especially important since the two authors differed so 

 widely in their conclusions concerning the development of the 

 embryo-sac. My own results are somewhat different from either 

 and it has been possible to carry the study of the embryo further. 

 It, therefore, seems advisable to publish the results at this time. 



The material for this study was collected in a large lagoon 

 near San Antonio de los Bafios in the Province of Havana, Cuba. 

 It was killed and fixed in the following preparations : 



I. Chromo-acetic solution, 



Water 99 c - c - 



3 c - c - 



Glacial acetic acid 



Chromic acid 7 gram 



2. Picro-acetic solution, 



(a) Saturated aqueous solution of picric acid 99 c - c » 



Glacial acetic acid I c.c. 



(b) Saturated 70 per cent, alcoholic solution of picric acid ... 99 c - c * 



Glacial acetic acid . 

 3. Sulphuro-acetic solution, 



I c.c. 



(a) Saturated aqueous solution of picric acid 9° c - c - 



Sulphuric acid 



2 c.c. 



(b) Saturated 70 per cent, alcoholic solution of picric acid. . . 98 c.c. 



Sulphuric acid 



2 c.c. 



All these preparations were quite satisfactory but the picro- 

 acetic preparations were the best and the aqueous solution better 

 than the alcoholic. 



The greater part of the work was done in the laboratory of 

 the New York Botanical Garden and specimens of the plant have 

 been deposited in the herbarium of that institution. 



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