4' 4' 4 JtemarJcs arid Observations suggested 



progeny, and the other subjects noticed in these sections, are full 

 of information. 



In the section Growth by the Root, some have contended 

 that the young spongioles of the root wei'e incapable of con- 

 ducting sap, and that it was only after their organisation was 

 completed that they were of any use ; but the plain doctrine laid 

 down by the professor, that the young spongioles, so soon as 

 formed, commence their functions, tallies best with experience. 

 The fact noticed, that the young spongioles are found to be rich 

 in nitrogen, shows the benefit of keeping the soil open to admit 

 air freely, the great source of nitrogen. The young spongioles 

 of the root being the great source of nourishment to plants, 

 every means should be used to increase them. In soil made free 

 by manure, the interstices left encourage the fibres to run among 

 the soft manure ; and turf in the act of decomposing is still 

 better. The old thatch and turf from a house cause plants to 

 root and grow luxuriantly; but the greatest promoter of roots is 

 well-rotted leaf mould : if a handful is put round the roots of a 

 pot plant, that is wished to be encouraged to root, it soon 

 jbecomes like a wig. On the excrement by the roots, I formerly 

 sent you a paper on a substance apparently excreted by the 

 roots of spruce and Scotch fir. It sometimes, as I noticed there, 

 appears to run in threads like a fungus. There is no notice of 

 any fungus on the roots of any of these trees in the Encyclopcedia 

 of Plants. There is one noticed as occurring on the roots of 

 oaks, and a white substance, something partly resembling these 

 in its appearance, is sometimes found on the oak ; but it only 

 occurs on some plants, not all, and in small quantities ; whereas, 

 in the spruce and Scotch fir, it is on every plant, even on the 

 very youngest seedlings when newly sprung, clinging to the 

 minute spongioles, having every appearance of having issued 

 from the pores of the skin : perhaps there may be both an 

 excrement, and a parasitical fungus growing on the excrement. 

 On the propagation by the root, noticed in the same section, 

 those roots which abound in milky juices, as the genera i^hus, 

 ^uphorbm, Nuttalh'^, Papaver, Sic, will produce buds most 

 readily ; the harder, drier roots, as Cydonia, roses, plums, &c., 

 with more difficulty ; while small hard wiry roots cannot be 

 made to do so at all. In general, it will be found that plants 

 which are most diflicult to propagate by layers and cuttings 

 propagate best in this way. The rest of this section, and that 

 on growth by the stem, is very interesting, plain, and easy to 

 be understood. The reader is not confused with a detail of 

 beaded and spiral vessels, trachese, &c. : the plain doctrine of 

 the woody, fibrous, or perpendicular tissue, and the spongy, 

 cellular, or horizontal tissue, with the pressure of the latter 

 into medullary rays, thus opening a communication through 



