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268 OBSERVATIONS ON PLANTS

The third point of agreement is the adhesion of the funicuU imibihcales to the septum. This adhesion, though really existing, is not very obvious in the monospermous cells of Koniga maritima ; but in the supposed variety of this species from TenerifFe, in which the cells are occasion- ally dispermous, it is manifest, and is very remarkable in all states of Koniga libyca.

I first introduced this adhesion of the fanicnli to the septum as a generic character in distinguishing Petrocallis from Draba. It has since been advantageously employed in the character of Lunaria by M. De Candolle, who, how- ever, supposes this structure of much rarer occurrence in 210] Cruciferoe than it really is. According to my observations, it is neither unfrequent, nor always of generic importance. Thus, I find it to exist in some species only of Arabis, namely A. Turrita, pendula, and canadensis, and hence I did not introduce it into my generic character of Parrya, though I have noticed it in my description of the species.

The principal difference existing between these t\v'o species of Koniga is that the cells of the ovarium and silicula of K. maritima are monospermous, while those of Jibyca are polyspermous, the number being variable, appa- rently indefinite, but not exceeding six. There are, how- ever, other instances in this family, in wdiich the mere dif- ference betw^een definite and indefinite number of seeds is of specific importance only, as in Draba and Meniocus, in each of which a species exists with dispermous cells ; and the objection arising from the apparently still greater dif- ference between unity and indefinite number in the two species of Koniga is removed by a supposed third species or variety of K. maritima, in wdiich two seeds are occasion- ally produced in each cell. It may even be observed that from unity to the indefinite number in this case, where the ovula in the different cells are alternate, the transition is perhaps more easy than from the binary to the indefinite, in cases where, as in Alyssum properly so called, the ovula are placed opposite in the different cells, and are in the same cell equidistant from its apex ; this symmetry, pro- bably, admitting of addition only by fours.

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