CALIFORNIA ACADEMY OF SCIENCES. 73 



more conspicuously toothed, and the bristles of the pod 

 uncinate. — Tftysanocarpus pusillus. Hook. Icon. t. 42. 

 Torr. & Gray. Fl. N. Am. I. 119. Hook & Am. Bot. 

 Beech. 324. Watson, King's Hep. V. 31, and Bot. Cal. I. 49. 

 T. oblongifolius. Nutt. Torr. & Gray 1. c. 



Without any hesitancy do I separate this very common 

 plant from the beautiful genus, Thysanocarpus, of which it 

 has neither the habit, nor the technical character. The 

 stems of Thysanocarpi are firmly erect, and simple up to 

 where they part into several racemose branches which are 

 also erect. Their leaves are in a radical, rosnlate tuft mostly, 

 and their pubescence is simply hirsute, none of the hairs 

 being forked even, much less stellate. Their pods consist 

 of strongly plano-convex, completely indehiscent, cartilagi- 

 nous nutlets, the widely radiating fibres of which are connect- 

 ed by a hyaline membrane, thus forming a broad, encircling 

 wing. Athysanus has its pods not only marginless, but the 

 firm, slightly woody interior part, so far from combining 

 inseparably into a solid shell, consists of two slightly, 

 although equally convex valves which separate from one 

 another completely, when moisture and warmth have caused 

 the swelling of the seed. The fruit is therefore less worthy 

 of being described as indehiscent than is that of Hetero- 

 draba, in which the valves, even when soaked, separate less 

 regularly and less readily. 



Should further and more careful examination of fresh and 

 immature specimens reveal in any instances more than one 

 ovule, so that the pods would need to be described as by 

 abortion 1-seeded, an event which I half anticipate, inasmuch 

 as it occurs in some foreign genera of cruciferoe, then would 

 Athjsanus be fairly reducible to Heterodraba, which it looks 

 so exceedingly like, but from which it is, for obvious struc- 

 tural reasons, at present deemed needful that it shall be 

 held distinct. The place for these two genera would seem 

 to be near each other, between Alyssum and Draba, as rela- 

 tives of them, although anomalous by their nearly or quite 

 indehiscent pods. 



