STR 



pulate, furnished ■with stipules ; and 

 exstipulate, having no stipules. 



STOLE {stolo, a shoot or scion). By 

 this term some botanists have designated 

 that kind of branch of plants, which 

 differs from the soboles or sucker in pro- 

 ceeding from the stem above the surface 

 of the earth, into which it afterwards 

 descends and takes root, as in aster 

 junceus. By the older botanists, a 

 sucker was always understood by the 

 word stoloy and surculus indicated a 

 vigorous young shoot without branches. 



STOMATODA (aro/xa, a mouth, ttoi'v, 

 9ro36r, foot). A group of the crustacea, 

 in which the cephalic segment is free, 

 and supports large pediform maxillae. 

 In these animals the branchiae are at- 

 tached to natatory post-abdominal feet. 



STO'MATE (o-TOMa, a mouth). The 

 botanical name for an oval space, lying 

 between the sides of the cells in the epi- 

 dermis of plants, and opening into a 

 cavity in the subjacent tissue. 



STONESFIELD SLATE. Slaty cal- 

 careous limestone ; a constituent portion 

 of the Lower Oolite formation, abound- 

 ing in organic remains. 



STOOL {stolo^ a shoot or scion). A 

 term applied in Botany to the parent 

 plant from which young individuals 

 are propagated by the process of layer- 

 ing, as it is technically called by bo- 

 tanists. 



STOURBRIDGE CLAY. A variety 

 of clay with the general properties of 

 potters' clay, but of a dark colour, em- 

 ployed in the manufacture of crucibles. 

 It appears to have originated from the 

 disintegration of shale. 



STRAIGHT LINE. According to 

 Plato's definition, " a straight line is that 

 of which the middle parts hide the ex- 

 tremities," the eye being placed in the 

 continuation of the line. Archimedes 

 defined a straight line as " the shortest 

 distance between two points." Euclid 

 defines it as " that which lies evenly be- 

 tween its extreme points." These are 

 all very amusing definitions |o those who 

 Jcnow what a straight line'TsTTor 'tlie 

 rest, it may be sufficient to say that •' a 

 straight line is a straight line." 



STRAIT. A narrow channel connect- 

 ing two seas together, or a sea with the 

 ocean, as the strait of Gibraltar. 



STRATIFIED ROCKS. Rocks ar- 

 ranged in strata or beds, supposed to 

 have been so deposited by water. Under 

 the terms Primary, Secondary, and Ter- 

 tiary Strata, the characters of these rocks 

 317 



STR 



are described. Other particulars willDe 

 found under the term Stratum. 



STRATUM {stratum, a layer or bed, 

 from sterno, to spread out). In the lan- 

 guage of Geology, a stratum is a bed or 

 mass of matter spread out over a certain 

 surface by the action of water, or, in 

 some cases, by wind. The deposition of 

 successive layers of sand and gravel in 

 the bed of a river, or in a canal, affords a 

 perfect illustration both of the form and 

 the origin of stratification. A large por- 

 tion of the masses constituting the earth's 

 crust are thus stratified, the successive 

 strata of a given rock preserving a gene- 

 ral parallelism to one another ; but the 

 planes of stratification are not perfectly 

 parallel throughout a great extent, like 

 the planes of cleavage. See Rock. 



1. The inclination of strata from the 

 horizontal position is called the dip. The 

 direction, or line of bearing, of strata is 

 called the strike, and it is indicated by a 

 horizontal line at right angles to the dip. 

 When strata protrude above the surface, 

 or appear uncovered, they are said to 

 crop out. They are said to be conform- 

 able, when their planes are parallel, what- 

 ever their dip may be; unconformable^ 

 when a set of strata is so connected with 

 another, that the planes of stratification 

 of the one series have a different direc- 

 tion from those of the other series. See 

 Fault. 



2. Strata, recent or alluvial. Under 

 this terra are included all those deposits 

 which have resulted from the action of 

 the elements, or from the progress of 

 vegetation, in the course of the period 

 which has commenced after the depo- 

 sition of the tertiary strata, and has con- 

 tinued to the present day. They may be 

 arranged under the heads of alluvial de- 

 posits, concretionary deposits, coralline 

 deposits, and vegetable deposits. These 

 terms will be found in their respective 

 places. 



STRATUS (Lat. a bed or covering). 

 The fall-cloud ; a primary foim of cloud, 

 which rests upon the surface of the earth. 

 It varies in extent and thickness, and is 

 generally formed by the subsidence of 

 vapour in the atmosphere. This form 

 comprises all those fogs and mists which, 

 on summer evenings, fill the valleys, 

 remain during the night, and disappear 

 in the morning. Hence it has been called 

 the cloud of night. The stratus must be 

 distinguished from that variety of the 

 cirro-stratus which resembles it in exter- 

 nal characters : the former does not wet 

 P3 



