CRUCTFERiE. 39 



order to lay bare the embryo, and observe the position of the radicle on 

 the cotyledons, which is now considered as the most essential among 

 the generic characters. 



A few terms specially made use of in describing plants of this family 

 may require some explanation. The calyx is said to be bisaccate when 

 two of the sepals, a little outside the two others, are broader at the 

 base, forming little protuberances or pouches. The pod is termed a 

 siliqua or siliqiiose when linear, at least three or four times as long as 

 broad ; a silicule or siliculose when short and broad — not twice as long 

 as broad; and a lomentum or lomentose when it does not open in valves. 

 The nerves on the pod, often used as a generic character, can be best 

 seen on dried specimens ; they are even sometimes quite imperceptible 

 on the fresh pod. The seeds are said to be in one roiv when, from the 

 narrowness of the pod or the length of the seed-stalk, they occupy the 

 centre of the cell, the two rows being as it were blended into one ; or 

 in two rotes, when the two rows are distinct without overlapping each 

 other. In the embryo, the radicle is said to be accumbent when it is 

 bent down on the edge of the cotyledons, incumbent when bent over 

 the back of one of them ; in the latter case the cotyledons are either 

 flat or conduplicate, that is, folded longitudinally over the radicle. 



It must be admitted, however, that, notwithstanding all these nice 

 distinctions, the genera of Crucifers, as at present defined, are often 

 as artificial as they are difficult. But as the remodelling them is not a 

 work to be undertaken in a local Mora, I have selected, from those 

 adopted in the best modern Floras, such as have appeared to me the 

 most natural. The following Table is founded, as much as possible, on 

 less minute characters, but even in the few British species it is feared 

 that the examination of the seed cannot always be wholly dispensed 

 with. 



rPod with a longitudinal partition, generally opening in two valves . . 2 

 1-j Pod not dehiscent, with one seed, or with several seeds placed end to 



L end and separated by transverse partitions (Lomentose) . . , .30 

 9 J Pod at least 3 or 4 times as long as broad (Siliqttose) 3 



I Pod not 3 times as long as broad (Siliculose) 15 



o q / Flowers white, purple, or red (never yellow) .... 4 

 I Flowers yellow 11 



r Petals large, on long claws, purple or rarely white. Stigmas 2, very 

 4 -I short, erect and parallel ,5 



I Petals small, or the claws scarcely longer than the calyx. Stigma entire 6 



r Leaves hoary and soft. Stigmas thickened at the base. (Cotyledons 

 - j accumbent) 1. Stock. 



i Leaves green, with coarse hairs. Stigmas not thickened. (Cotyledons 



<- incumbent) 8. Hespekis. 



fi f Leaves all undivided 7 



I Leaves, at least the lower ones, pinnate 8 



