696 REPORT— 1891. 



8. Notes ov, Infernal Fhlocni in the Dicotyledons. Bij D. H. Scott, M.A., 

 Fh.D., F.L.S., Assistant Professor in Biology {TJotany), Boyal CoUege of 

 Science, London. 



The questions discussed in this paper are : — 



(1) The relation of internal (or intraxylary) phloem to the vascular bundles and 

 to the pith. Do bicollateral bundles exist? Views of De Bary, Herail, Van 

 Tieghem, "Weiss, and Lamounette. Cases in -which internal phloem is accompanied 

 hv centripetal medullary wood. Significance of this. Phylogenetic importance 

 of Lamounette's view of the medullary nature of internal phloem. Bearing of the 

 question on general Dicotyledonous anatomy. 



(2) Systematic importance of internal phloem. Numerous orders in which 

 this character is constant. 



(3) Structure of the root in plants which have internal phloem in the stem. 

 Changes in the position of the phloem in the transitional region. Plants which 

 have internal phloem in the root. 



(4) Physiological significance of internal phloem with reference to recent views 

 as to the function of the phloem in general. 



4. On the Occurrence of Dlastnse in Pollen. 

 By Professor J. R. Green, M.A., B.Sc. 



Though recent researches have led to the discovery of the various points of 

 interest connected with the morphology of the pollen grain and the pollen tube, 

 but little attention has been giveu to tbe details of its physiology. It is known 

 that the contents of the ripe grain, besides its protoplasm, include proteid and 

 carbohydrate bodies, tiie latter being in part starch, in part some form of sugar. 

 That these are reserve materials, intended to be used during the growth of the 

 pollen tube, seems to admit of no question. Indeed Van Tieghem has shown that 

 like other storehouses of reserve materials, the pollen grain of some plants contains 

 certainly one ferment or enzyme leading to the utilisation of these stores, the fer- 

 ment invertase which is capable of inverting cane sugar. 



Starch being of such frequent occurrence in pollen, attention was directed in 

 the experiments now briefly to be summarised to the possibility of there being also 

 present some form of diastase. The pollen taken for investiga'tion was that of the 

 lily and that of the sunflower. A starch paste of about 1 per cent, strength was 

 the medium on which to test the action. In the first experiments the contents of 

 one ripe anther of a lily were mixed with 5 c.c. of this paste and exposed in a test 

 tube for some hours to the temperature of about 20° C. A precisely similar 

 tube was boiled and set aside with the other to serve as a control. The diastatic 

 action slowly became evident, the unboiled starch paste passed through the several 

 stages of soluble starch and dextrin to sugar, the boiled one remaining unchanged. 

 Sunflower pollen gave a similar result. 



Diastatic action being so established, it remained to see whether diastase itself 

 was present or whether the change was brought about by the pollen grain apart 

 from such a body. Diastase being readily soluble in water or in glycerine, an 

 attempt was made to prepare it from the pollen cells. A quantity of the pollen of 

 the sunflower was collected and ground up between two glass surfaces with some 

 dilute glycerine. When the pollen was completely broken up, as shown by 

 microscopical examination, it was left in contact with the glycerine for twelve 

 hours and then filtered free from debris. 



A similar experiment to the first was then arranged, the glycerine extract being 

 used instead of the pollen grains. In this case again, in the unboiled tube the 

 starch grada.ally disappeared by the usual stages, and there was simultaneously a 

 gradual and increasing appearance of sugar. 



The germination of the pollen grain thus, so far as its reserve of starch is con- 

 cerned, proceeds upon the same lines as the germination of the complex bodies 

 which we know as seeds. 



