404 



NATURAL HISTORY OF PLANTS. 



a quite peculiar organization. It is known (chiefly through the 

 researches of H. Mohl) that in Protectees generally the stomates are 

 very small, and are situated, not at the surface of the epidermis, but 

 at the bottom of a sort of pouch or well, as deep as the epidermis is 

 thick, and with the circular or elliptical external opening sensibly 

 contracted. The nervation of the leaves is also often characteristic. 

 It is pinnate, rarely palmate ; the secondary ribs radiate sometimes 

 from the base of the blade, sometimes at a certain distance up, like 

 the rays of a fan. The terminal veinlets are usually arranged in an 

 elegant delicate network, sometimes very complicated. 1 The leaves 

 often degenerate near the flowers into involucrant bracts, which 

 become more and more coloured and simple in form, and recall, in 

 their tint and approximation and in the way they protect the 

 flowers, the leaves of the involucre of Composite and some allied 

 types. 2 



Affinities. — The order Protectees, placed by A. L. de Jussieu in 

 Jpetcdce, was left there by all authors until A. Brongniart, 3 fusing 

 this class with Potypetats, placed Protcines between Rhamnoides 

 and Daplmoides, — i.e., next the three classes which he terms 

 Mi/rtoidcce, Rosines, and Leguminoss. Lindley 4 puts Protectees in 

 his Alliance XLI {Dap finales), just before Rosettes which includes 

 Rosacea, Pomaces, Dr/tpaces, Fabaces, and Chrysobalanaces. In the 



1 It is from these characters that authors have 

 thought they could distinguish leaves of Prota- 

 ceous plants in geological strata (see Ettings- 

 hai'sen, Proteac. der Vorwelt). Hence a 

 detailed study has been made of the nervation, 

 which is thus described by De SAroRTA (in Ann. 

 Sc. Nat., ser. 4, xvii. 248) : "The tertiary ribs, 

 always more or less oblique to the secondary, 

 ramify by bifurcating to their last subdivisions ; 

 the network resulting from the intersection of 

 the ramifying venules gives rise to rhomboidal, 

 trapeziform. or hexagonal meshes, that vary in 

 size, proportion, and regularity with the genus 

 and species. These tertiary veins, oblique to the 

 secondary, are more or less so according to the 

 obtuseness of the angle which the latter make 

 with the midrib." Hence the leaves are divided 

 into those which have oblique ribs {Greiillea, 

 Lomaiia, Leucospermum, &c), and those in 

 which the secondary ribs are given off at an 

 obtuse or nearly a right angle {Xylomelum, 

 Kniqhtia, BanKsia). These considerations have 

 led geologists to admit fossil types of Protectees, 



such as Leueadend rites, Banksltes, Palaoden- 

 dron, Lomatites, Knightites, Myricop/iyllum, 

 Rltopaluxpermites (Sap.), Emlothrites, Driait- 

 droides (Ung.), as well as true Orerilleas and 

 Jlakeas. Protectees are given as " the most 

 ancient dicotyledonous type [excluding, of course, 

 Ci'iiiferee] whose presence it is possible to ascer- 

 tain in the fossil state." It is in the Senonian 

 beds of the Aachensandstein [Sandstone of Aix- 

 la-Chapelle] that the preponderance of these 

 types is most marked, some hundred species 

 being admitted. Later on, it is said, in the 

 tertiary beds, true P/ryandras are found, and 

 then the Protectees commence to diminish in 

 number, and seem to be replaced by Myricaces 

 (see Sap., op. cit., 29S ; xix. 21, 58, 109; ser. 

 5, iii. 19, 24, 30, 33, 55, 59, 95, 144). 



2 It is more on account of the coloured invo- 

 lucres than the flowers that Protectees are so 

 ornamental in the conservatory or winter garden. 



3 Enum. des Gear, de PI. Cult. (1843), 120. 



4 Veg. Kingd., 529. 



