613 



discoloured. This led me to examine carefully the so-termed " mar- 

 ginal vein," which proved to be an open continuous channel of pe- 

 culiar structure, extending from the base to the top of the leaf, alto- 

 gether different from the vascular tissue constituting the proper veins, 

 but no doubt in communication with them, and serving as the reci- 

 pient and conductor of the fluid conveyed by them from the root. 

 It is sufliciently wide to admit a bristle, which may be passed up it 

 without the aid of a lens. On cutting a leaf across with scissors, the 

 fluid escaped from the midrib and veins, but less plentifully than from 

 the marginal channels. One leaf, which had recently expanded, and 

 had its cylindrical point unfaded at the extremity, did not give out 

 any fluid, nor was there any escape from the flower : with a micro- 

 scope I could not detect any pore or valve, such as is stated to exist 

 in Limnocharis Plumieri ; hence I am inclined to infer that the exu- 

 dation does not take place, even in a close humid atmosphere, until 

 some previous natural decay of the cylindrical point of the leaf. 

 Those who have the means of proving the contrary are requested to 

 pursue the enquiry. It may be proper to add that an escape of fluid 

 was observed at the back of two of the leaves, whose extremities 

 were so curled as to admit of a lodgment of the water in that position, 

 and that a quantity of the fluid, collected on glass and suffered to eva- 

 porate, left behind it only faint traces of mucilaginous matter. The 

 opinion entertained by some, that spiral vessels convey air and not 

 fluid, will derive little support from an examination of this plant.— /^L 

 306. On the buds of Rohinia Pseudacacia. One fine evening last 

 summer, during one of those welcome intervals of relaxation which 

 are afforded by the visits of an esteemed friend, we happened to stroll 

 under the shade of this tree, when a happy collision of ideas directed 

 our joint attention to its well-known property of suddenly, putting 

 forth its foliage, late in the spring, without any previous warning. 

 On cutting across one of the petioles, near its base, with a sharp pen- 

 knife, I was struck with the appearance of an open cavity lined with 

 stiff" white pubescence ; and as there was no trace of an external ax- 

 illary bud, it instantly occurred to us that this tree resembled Platanus 

 in its mode of vegetation. Longitudinal sections of this part were 

 forthwith submitted to the microscope, when lo ! instead of a solitary 

 bud, no less than three were contained in the hollow base of each 

 petiole, one placed immediately below the other, the lowest in a state 

 of less perfect formation. It remained to enquire, at the proper sea- 

 son, whether or not two of the three buds were abortive, and I have 

 recently directed my attention to this matter. The uppermost bud, 



