824 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the nature of the pericycle of the stem and leaf, which is always 

 reduced to a single layer of thin-walled cells. 



The Umbelliferse and Araliaceee are characterized by the invariable 

 presence of a secreting system of canals in the pericycle, frequently 

 superposed on a second system situated in the parenchyma. If this 

 character is adopted, the genera Mastixia, Helwingia, and Gurtisia 

 must be excluded from Araliacese. These two orders, together with 

 the PittosporesB, constitute a group distinguished from the whole of 

 the rest of the vegetable kingdom by the arrangement of the secreting 

 canals in the root, and the displacement which this causes in the 

 insertion of the secondary roots ; the PittosporeyB differing from the 

 other two orders in their superior ovary. In this respect, however, 

 Ancistrocladus furnishes a connecting link. 



In the Clusiacese the embryo is abundantly provided with secret- 

 ing canals, affording a remarkable example of a secretion produced 

 abundantly in the embryonal condition. The Ternstroemiacese are, as a 

 rule, destitute of these structures, though the rule is not without 

 exception. The Hypericacese are characterized by the presence of 

 narrow oleiferous canals in the pericycle, whenever this remains 

 parenchymatous, i. e, always in the root, as well as in the stem in the 

 typical herbaceous species. In other respects this order shows close 

 affinity to the Clusiacete. The resiniferous cavities of the Myrsinaceas 

 are localized in the stem and leaf, never occurring in the roots. The 

 Dipterocarpeag are distinguished by the presence of oleiferous canals, 

 and by the exclusive localization of these canals in the primary and 

 secondary wood. 



Details are given with respect to the structure and arrangement 

 of the secreting canals in some other less important natural orders, 

 making 18 in all ; and the results given in previous papers are again 

 included. 



Peculiar Structures in the Flesh of the Date.* — Prof. W. A, 

 Tichomirow describes structures in the flesh of the date, the nature 

 of which he is not able to determine, similar to those found by 

 Fliickiger in the fruit of Bhamnus cathartica. They are insoluble in 

 water, not doubly refractive, coloured yellow by iodine and sulphuric 

 acid, cobalt-blue by chloride of iron, green or olive-green by Millon's 

 reagent, olive-green by ammoniacal cupric oxide, blue-violet or red- 

 violet by caustic potash. 



Anatomy of Euphorbiaceae-j — Herr F. Pax discusses this subject 

 in relation to the classification of the genera in the order. Bicollateral 

 vascular bundles are found in all the Crotonese ; occasionally in all 

 the rest of the groups except the Stenolobese, Phyllantheas, and 

 Brideliege. The Euphorbiaceae may be divided into four groups 

 according to the degree of development of the latex-vessels, viz. 

 (1) Latex-vessels entirely wanting; the secretion being distributed 



* SB. Intemat. Congress f. Bot. u. Gartenbau, St. Petersburg, May 1884. See 

 Bot. Centralbl., xxi. (1885) p. 222. 



t Engler's Bot. Jahrb., v. pp. 384-421 (2 pis.). See Bot. Centralbl., xxi. 

 (1885) p. 326. 



