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Additional Answers of Dr. Tonge to some of the Queries about Vegetables, printed in Numb. 43.
TO the 11th.I add, that the Sap (e.g.) of a large Walnut in the latter season of its running, i.e. when it yields no sap any longer in the Body or Branches at any time of the day, runs longer at the roots on the South or Sunny-side, than on the North or shady side.
To the 12th.Birch-trees bored in the Spring so late, in respect both of the year and day, that they have afforded no Sap at all at the body, have been found sometime after, to have issued such plenty of juice, as hath condensed in the hole to a stiff jelly. This I suppose to have risen not about Autumn, (as some conjecture) but in the heat of some day the same Spring, or in some extraordinary hot day following after that tryal, or the hole to have been made too late in the evening after the tree hath ceased to run for that day: Or else it hath in some favorable season run earlier than ordinary in the Spring following. But this is left to farther tryal; as also, Whether the sap in trees, e.g. in Maples, will not run some dayes sooner at the roots, than at body and branches; as they also run at roots some dayes longer than at body and branches.
To the 13th.As plenty of Rain can cause no more plenty of Sap than the pores of the root, body and branches will admit; which must stay some time to be digested, and converted into nourishment: So too much cold rain may by over-cooling hinder the Sap, by abating from the degree of heat necessary to pulsion of Sap into the root, and to the digestion in the tree; which is also in watering. On this ground it seems probable, that drawing Sap constantly from trees every year, will not hinder their growth in body, branches, leaves, nor fruit, to any great prejudice; for, pulsion will still supply juice into the emptied pores, till their capacity be filled.
It is possible also, that trees may grow better, and give more fruit, if the right art of drawing sap be found out for that end; as some persons grow fatter by often Bleeding. If plenty of Sap drawn from trees hinder at all, it seems probable, that it will hin-
