204 THE PHENOMENON OF 



beautiful and peculiar aspect. The formation and sub- 

 sequent solution of the oil, as I have observed it in these 

 little plants, is not connected, as in the preceding exam- 

 ples, with formation of spores, but occurs in the vegetative 

 cells ; the formation of seed, in 'Penium curtum, doubtless 

 taking place through conjugation, has not yet been 

 observed. In fresh vegetating individuals the contents 

 of the longest cell, somewhat constricted in the middle, 

 exhibit the following character : in the middle of the cell 

 exists a rarely clearly distinguishable nucleus ; in the 

 middle of each half a large globe, which Nageli calls a 

 chlorophyll-vesicle, but which I found completely filled 

 with starch, at least certainly in older cells. The rest of 

 the light-green general mass of the contents is traversed 

 in each half by ten to twelve darker green , somewhat granu- 

 lated longitudinal bands, which, seen from the apex of the 

 cell, appear like thickish plates, arranged radiantly around 

 the long axis, and united in the middle. If Penium 

 curtum is cultivated for a length of time in a dish of 

 water, all the individuals undergo a peculiar alteration, 

 some sooner, some later. The dark-green longitudinal 

 streaks become indistinct and irregular, tiU at length 

 they disappear, while a quantity of lighter and more 

 brilliant globules appear, which, increasing in size, wholly 

 displace the green contents of the cell, so that the pre- 

 viously bright green cell at last assumes a pale, dirty 

 yellow aspect. Accurate examination shows that the 

 brilliant globules now filling the cells are not the spores, 

 as might perhaps be conjectured, nor starch-grains,* 

 but really drops of oil. Tincture of iodine scarcely per- 

 ceptibly alters their colour, while the two large globules 

 of starch still existing in the two halves of the cell acquire 

 a dark violet tint. If oil of turpentine is applied to a 

 specimen not quite dried up, the globules of oil coalesce 

 into larger irregular drops ; when more completely dried 



* Meyeii observed the cell oS Closienmii Lunula densely filled with staroli 

 grains, (' Pflanzenpli.,' iii, 137.) 



