TRANSACTIONS OF SECTION K. 815 



bundles can be traced in the stem of about thirty dicotyledonous orders, and no 

 doubt many moi-e will reveal it. 



Other characters very frequently accompanying the above feature in dicotyle- 

 donous stems are : — 



(a) V-shaped xylem ; (b) reticulate and circular phloem ; (c) bundle often 

 concentric, with central circular phloem, and when collateral often with irregular 

 orientation ; (d) few, large vessels in xylem ; (e) bundle rounded or elliptic and 

 enclosed in sclerotic sheath ; (/) very small development of cambium ; (5^) laro-est 

 bundles occur nearest centre of stem, the smallest nearest the periphery ; (/i) rudi- 

 mentary character of many bundles, representing those members of the vanishing 

 scattered system which are not destined to form part of the functional cylinder ; 

 (i) limit between cortex and cylinder marked by a sclerotic zone ; (j) cortical 

 system of bundles which are often concentric in structure ; (k) trimerous character 

 of some or all of the floral whorls; (/) several orders exhibit 5-merous single 

 perianth-whorl in flowers which, as Celakovsky has shown, is derived from 

 two trimerous whorls by conversion of lowermost perianth-member into a bract. 



In some monocotyledons the scattered bundles have become very peripheral 

 and even reduced to a single series or row of bundles. 



In some cases amongst dicotyledons where the scattered arrangement has 

 vanished from the stem it can still be found in the less modified foliao-e-leaf 

 especially where the petiole is cylindric in contour or possesses a considerable 

 diameter. 



In view of the above facts the author cannot agree with those writers who 

 maintain that the vascular structure of the seedling stem of dicotyledons generally 

 proves it to be primitively tubular in character. The same will, for reasons above 

 set forth, apply to the case of monocotyledons. 



A series of slides accompanying this paper illustrates the main feature of the 

 subject in the stems, &c., of plants belonging to many natural orders. 



3. The Composition of the Flora of the North-east of Ireland. 

 By R. Lloyd Praeger. 



The counties of Down and Antrim form the most easterly part of Ireland, and 

 the portion which most nearly approaches to Scotland. Their combined area is 2,148 

 square miles, and their flora numbers 820 species of flowering plants and vascular 

 cryptogams, Antrim yielding 778 species, Down 752 ; the total flora of Ireland 

 bemg reckoned at 1,020 species, and the average number occurring in an Irish county 

 accordmg to present knowledge, at between 630 and 640. Down is formed of 

 slates and granites, Antrim mainly of basalts. Limestone is very sparingly repre- 

 sented, and while the number of calcifuge plants in the flora is large, the calcicole 

 group IS poorly represented. With regard to the types employed by Watson to 

 show distribution in Great Britain, there is in the local flora an almost complete 

 representation of British type plants. English type plants are rather poorly 

 represented, and are more plentiful in the Antrim than in the Down flora. 

 Scottish type plants reach in Antrim their maximum for Ireland ; in Down they 

 are somewhat fewer. Of Highland type species there is a fair representation as 

 compared with other Irish counties of similar character ; Antrim, thouo-h of less 

 elevation, contaius more alpine plants than Down. Germanic plants are extremely 

 few in Ireland, being only thirteen in number; of these the district yields but 

 four. In Atlantic type plants Down and Antrim are comparatively rich. 



Turning to the types of distribution which the reader has recently proposed 

 for the Irish flora, we find the district is naturally very poor in Central type 

 plants, which are largely calcicole and marsh species ; while Mumonian and 

 Connacian species are practically absent. Marginal type plants, on the other 

 hand, are very largely represented, while of Ultonian species Antrim is con- 

 spicuously the focus, Down being considerably poorer. Lagenian plants are only 

 tolerably represented, their focus lying farther to the southward. 



