10 HOFFMANN ON THE CIRCULATION 



only less perfect in general here, but also takes place in an in'c- 

 giilar manner, by no means in one and the same plane (parallel 

 to the surface of the section). This tuberous bulb is, evidently, 

 remarkably well fitted to afford a clear notion of the organs con- 

 veying the sap in plants, since here all the important parts, the 

 spiroids, the parenchyma, the elongated vessels, and the liber, 

 are distinctly, and in fact — as in the Dicotyledons — widely sepa- 

 rated from each other, to the great convenience of the observer. 



Underneath the bulb is the true root, which is of a pointed 

 conical form. Here also the vascular bundles lie in the middle, 

 while the blue colouring occurred in the parts more toward the 

 circumference. In the stem no discoloration could be perceived, 

 even in the cases where distinct reaction occurred, not only in 

 the bulb below, but also in the capsule at the upper end. From 

 this it seems as if the absorbed sap rested or became accu- 

 mulated in particular parts of the plant, while it only hurried 

 through the others as passages. In the cases where reaction 

 was observed in the calyx, microscopical examination showed 

 that the air-carrying, delicate unreliable spiral vessels or annular 

 vessels were never the organs conveying the sap, but the elon- 

 gated cells often lying close beside them. In specimens which 

 were taken up nine days after watering, the absorbed ferrocyanide 

 could be detected inside the half-ripe, otherwise fully-developed, 

 capsules. It occurred within the elongated cells, which always 

 accompanied the numerous delicate air-vessels in the axis, and 

 seen through a lens after the reaction, formed a great abundance 

 of little blue points and streaks. The soft, unripe seeds also exhi- 

 bited distinct reaction in particular places ; here the fluid had 

 also been conveyed from cell to cell through the seeds; no 

 vessels of any kind exist in the seeds. 



Tigridia pavonia, Pers. (Iridaceae). — The plant was watered 

 with the ferrocyanide while in full vegetation, on the 25th of 

 July. After six days the reaction was observable not only in the 

 bulb but also throughout the whole stem up to the floral organs, 

 but not in these or in the interior of the germen. In nine days, 

 however, the germen also had absorbed the salt, close beneath 

 the surface, but neither the interior nor the ovules exhibited any 

 reaction. The current had advanced more externally to the 

 upper i)arts, to supply the floral organs with sap in the first 



