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 264 OBSERVATIONS ON PLANTS

of the order that may be called Brassice^s, but which is much more extensive than the tribe so named by M. De Candolle ; including all the genera at present known with conduplicate cotyledons, as well as some others, in which these parts are differently modified.

There are tAvo points in the structure of Savignya, that deserve particular notice. I have described the aestivation of the calyx as valvular ; a mode not before remarked in this family, though existing also in Ricotia. In the latter genus, however, the apices of the sepals are perhaps slightly imbricate, which I cannot perceive them to be in Savignya.

The radicle is described by M. De Candolle as superior wdth relation to the cotyledons. I am not sure that this is the best manner of expressing the fact of its being hori- zontal, or exactly centrifugal, the cotyledons having the same direction. This position of the seed is acquired only after fecundation ; for at an earlier period the foramen of the testa, the point infallibly indicating the place of the future radicle, is ascendent. From the horizontal position of the radicle in this and some other genera, especially Parsetia, we may readily pass to its direction in Biscutella, where I have termed it descendent, a character which I introduced to distinguish that genus from Cremolobus. But in Biscutella the embryo, with reference to its usual direction in the family, is not really inverted, the radicle being still placed above the umbilicus. On the contrary, in CremoIobecB, a natural tribe belonging to South America, and consisting of Cremolobus and Menonvillea, though the embryo at first sidit seems to as^ree in direction with the order generally, both radicle and cotyledons being ascen- dent, it is, in the same sense, not only inverted, but the seed must also be considered as resupinate ; for the radicle is seated below the umbilicus, and also occupies the inner side of the seed, or that next the placenta — peculiari- ties which, taken together, constitute the character of the 213] tribe here proposed. It appears to me singular that M. De Candolle, while he describes the embryo of these two genera as having the usual structure of the order, should

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