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bnlli and form of these structures are not directly detenr ined by 

 the spaces which the leaves allow : obviously there are other modi 

 fying causes. It should be added that while hese expanded free 

 extremities graduate into tapering free extremities, not diiiering 

 from ordinary vessels, they also pass insensibly into the ordinary in 

 osculations. Occasionally, along with numerous free endings, there 

 occur loops ; arid from such loops there are transitions to the ulti 

 mate meshes of the veins. 



These organs are by no means comimn to all leaves. In many 

 that afford ample spaces for them they are not to be found. So far 

 as I have observed, they are absent from the thick leaves of plants 

 which form very little wood. In Sempervivum, in Echcveria, in 

 Bryophyllum, they do not appear to exist ; and I have been unable 

 to discover them in Kalanchoe rotundifolia, in Kleinia ante-eupliorbium 

 md JicoideSj in the several species of Crassula^ and in other succulent 

 plants. It may be added that they are not absolutely confined to 

 leaves, but occur in stems that have assumed the functions of leaves 

 At least I have found, in the green parenchyma of Opuntia, organs 

 that are analogous though much more rudely and irregularly formed. 

 In other parts, too, that have usurped the leaf-function, they occur, 

 as in the phyllodes of the Australian Acacias. These have them 

 abundantly developed ; and it is interesting to observe that here, 

 where the two vertically-placed surfaces of the flattened-out petiole 

 are equally adapted to the assimilative function, there exist two 

 layers of these expanded vascular terminations, one applied to tho 

 inner surface of each layer of parenchyma. 



Considering the structures and positions of these organs, as well 

 is the natures of the plants possessing them, may \ve not form a 

 shrewd suspicion respecting their function ? Is it not probable that 

 they facilitate absorption of the juices carried back from the leaf for 

 the nutrition of the stem and roots ? They are admirably adapted 

 for performing this office. Their component fibrous cells, having 

 angles insinuated between the cells of the parenchyma, are shaped 

 just as they should be for taking up its contents ; and the absence 

 of sheathing tissue between them and the parenchyma facilitates the 

 passage of the elaborated liquids. Moreover there is the fact that 

 they are allied to organs which obviously have absorbent functions. 

 I am indebted to Dr. Hooker for pointing out the figure- of two 

 such organs in the &quot; Icones Anatomical&quot; of Link. One oi them is 

 from the end of a dicotyledonous root-fibre, and the other is from 

 the prothallus of a young Fern. In each case a cluster of fibrous 

 cells, seated at a place from which liquid has to be drawn, is con 

 nected by vessels with the parts to which liquid has to be carried. 

 There can scarcely be a doubt, then, that in both cases absorption 

 is effected through them. I have met with another such organ, 

 more elaborately constructed, but evidently adapted to the same 

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