REPORT ON THE PHILOSOPHY OF BOTANY. 45 



from the general mass, which showed that some power kept 

 them united. Shortly after, four appendages, like knife-blades, 

 developed at equal distances upon the inner face of the cell, 

 and gradually projected their edges towards the centre, till at 

 last they divided the granular mass into four little triangular 

 bodies; when the appendages had completely united at their 

 edges, they divided the cavity of the pollen-cells into four di- 

 stinct boxes, which then began to rounden, and finally became 

 little spherical masses. Each of these was the rudiment of a 

 grain of pollen, subsequently acquired a membranous integu- 

 ment, hardened, became yellow, and thus arrived at maturity. 



What is perhaps most important in these observations is the 

 demonstration of the original organic continuity of all the parts 

 of the anther, against the statement of M. Adolphe Brongniart, 

 and also against what appears to be the opinion of Dr. Brown, 

 as far as can be collected from the manner in which he speaks 

 of the evolution of the pollen in Tradescantia virginica *. 



Although it is not directly shown by these observations whe- 

 ther the perfect grain of pollen has one or two integuments, — a 

 question that may still be said to be unsettled, — it nevertheless 

 appears from other instances that M. Mirbel admits the exist- 

 ence of an outer not distensible coat, and of an inner highly 

 extensible lining. A curious paper upon this point f has been 

 published by a Saxon botanist named Fritzsche. By means of 

 a mixture of two parts by weight of concentrated sulphuric 

 acid, and five parts of water, he found that the grains of pollen 

 can be rendered so transparent as to reveal their internal struc- 

 ture, and that the whole process of the emission of the pollen- 

 tubes can be distinctly traced. He describes the universal pre- 

 sence of two coatings to the grains of pollen; and he also finds 

 that the pollen contains a quantity of oily particles in addition 

 to tlie moving corpuscles, — a fact which has also been noticed 

 by Dr. Brown. 



Although the generalizations in this work are less satisfactory 

 than could be desired, it must nevertheless be considered a 

 most valuable collection of facts, and as containing the best 

 arrangement that has as yet appeared of the various forms un- 

 der which the pollen is seen. 



FertiUzation. — The road which some years since was so 

 happily opened by Amici to the discovery of the exact manner 

 in which vegetable fertilization takes effect, is every day be- 

 coming more and more direct. The doubts of those who could 

 not discern the tubes that are projected into the style by the 



* Ohservations vpon Orchideae and Asclcpiadfeae, p. 21. 

 t Bettrage T:iir Kenninu.s des Pollen. 4to. Berlin, 1833. 



