1865.] Botany and Vegetable Physiology. 269 



narrow. The duration of the blotting out of the spectrum in this 

 manner, though it was so small that it might perhaps be called instan- 

 taneous, yet occupied an interval of time which could be appreciated. 

 This interval did not differ greatly from 2-10ths of a second. The 

 disappearance of the spectrum was not observed to be preceded by any 

 failure of the blue or of the red rays ; but the spectrum appeared to 

 remain unaltered in the relative intensity of its different parts up to 

 the moment of extinction. The advance of darkness upon the 

 spectrum, since it occurred precisely in the direction of its breadth, 

 swallowed up the rays of different refrangibilities throughout the 

 whole extent of the visible spectrum. The difficulties which attend 

 the successful application of spectrum analysis to the heavenly bodies 

 are so great, that much importance ought not to be given to a single 

 observation of which the results are negative. A series of spectrum 

 observations of the occultations of stars, especially if the list in- 

 cluded some stars of greater brightness than s Piscium, might possibly 

 afford information of interest and value. 



III. BOTANY AND VEGETABLE PHYSIOLOGY. 



(Including Microscopic Botany.) 



Cell-Foxmation, or Cytogenesis, is still a subject of dispute among 

 Vegetable Physiologists. Mohl advocated the formation of cells by 

 the intrusion of a fold from the wall of the mother-coll, and this view 

 was also supported by Naegeli. Schleiden laid great stress on the 

 action of the nucleus, or cytoblast, in transforming the mucilaginous 

 or protoplasmic matter into a gelatinous envelope, which ultimately 

 became a membranous wall of a cell. Others supported a free-cell 

 formation similar to what is seen in the formation of sporidia in the 

 ascigerous fungi. Karsten has recently taken up the subject, and 

 says, that in every case the formation of cells is free, and that the 

 septa, or partitions, when in opposition with each other, arise from 

 these confluent membranes, and not from any development of the wall 

 of the mother-cell. 



Schacht has recently examined the spermatozoids in ferns and 

 their allies, in mosses, charas, algse, and fungi. He says that these 

 bodies are formed from the contents of the mother cell in the interior 

 of the antheridium ; that they consist of a soft cell-like body, with 

 two or more cilia, and having no cell membrane, but simply a proto- 

 plasmic layer, enclosing fluid and granules. There are three typical 

 forms of spermatozoids. 1. In Algae the spermatozoid is a minute, 

 elongated, rounded or pointed cell, with one, two, or more cilia, often 

 of different lengths. 2. In Equisetums and Ferns the spermatozoid 

 assumes the form of a flat band, which gradually widens from before 

 backwards, and is rolled up like a watch-spring in the parent cell ; 

 when liberated it assumes a closely twisted spiral form. 3. In 

 charas, mosses, and lichens the spermatozoid is sausage-shaped, and 



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