DK. SCHACHT, ON THE MICROSCOPE. 



225 



By means of the continued action of oil of lemons or oil of turpentine, 

 the contents of the above-mentioned pollen-grains are rendered so trans- 

 parent that the construction of both the small pedicel-cell, and of the 

 larger terminal cell, as well as their attachment to the wall of the ])ollen- 

 cell, may be clearly seen. (.S'ce figs. 117 and 118.) This mode of observa- 

 tion, however, affords no information with regard to the fissure underneath 

 the pedicel-cell. If, however, one or two drops of common sulphuric acid 

 be applied to the ])ollen when quite fresh, and a thin glass cover be placed 

 over it, the immediate a])pearance of the polleji-cell may be observed at 

 the spot destined for tlie egress of the pollen-tube ; it swells and protrudes 

 itself more or less rapidly, and in a more or less perfect condition, through 

 the cuticle, and lies exposed before the eyes of the observer. 



Fig. 121 represents a ripe pollen-grain of Picea vulgaris under nitric 

 acid, at the moment when the true pollen-cell (y) emerges at (x) : (c^) is 

 the cuticle showing two layers. Fig. 122 repre- 

 sents a similar pollen-grain under concentrated 

 sulphuric acid ; the pollen-cell and its contents 

 have disajipeared, leaving only some drops, pro- 

 bably of oil, behind in the cuticle. Figs. 123 

 and 124 represent the pollen-cell of two ripe 

 pollen-grains forced out of their cuticle by the 

 operation of nitric acid ; (a), (&), and (c) aie the 

 cells of the cellular body. 



The empty cuticle now exhibits its markinjs 

 still more beautifully. It is now seen that, as 

 well in Abies pectinata as in Picea vulgaris and 

 Pinus sylvestris, the cuticle is very strongly developed at the two excres- 

 cences, and still more so between them, opposite to the place of egress of 



( 



Ct"-<^2niIiIffiS!S^ 



Fia;. 122. 



Fig. 123. 



Fig. 124. 



the pollen-tube, at the point of attachment of the cellular body. At 

 the places where the cuticle is thus strongly developed, two layers may 

 frequently be clearly seen. The fissure between the pollen-cell and the 

 cuticle has now disappeared ; but three cells (and not two only, as in the 

 earlier stages) are always to be seen in the emergent pollen-cell, and these 

 three cells form the cellular body in its interior. (See a, 1), and c, figs. 

 118, 123, and 124.) The lowest of these cells [c) is generally the smallest, 

 and becomes united in its growth to the wall of tlie jiollen-cell ; which fact 

 is clearly seen by pushing the covering-glass backwards and Ibrwards : it 

 was this cell which at an earlier period formed the apparent fissm-e between 

 the cuticle and the pollen-cell. The contiguous cell (h), which is some- 

 what larger, and which has been hitherto called the pedicel-cell, supports a 

 third cell, viz., the terminal cell of the cellular body («). I have never 

 seen raore than three cells in Abies pectinata, Picea vulgaris, and Pinus 

 sylvestris ; but I have never failed to see any one of these three cells in 

 the perfect pollen-grain. 



Although I have not been able to trace the development of the cellular 

 VOL. III. Q 



