[Vol. 9 



236 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



the genus, and it has evidently appeared separately in the two 

 species mentioned since they are not closely related. In Caulan- 

 thus it would seem that flattened pods have been derived from 

 terete ones, and there appears to be no reason to imagine a differ- 

 ent sequence in Thelypodium. 



Although the length of the pods is not of great value in specific 

 determination, the average length is of considerable interest. The 



d 



These 



fr 



Other species with long pods are T 

 stenovetalum. T. Howellii. and T. i 



The 



last is in doubt, and since it may not belong in this genus it 

 scarcely deserves mention. Reduction in the number of seeds 

 has been found in another genus of this family (Lesquerella) to 

 be correlated with divergence from the ancestral type, and this 

 might be supposed to apply also to Thelypodium. Decrease in 



ber of 



f the pods is a crude measure of reductio 



primitive and short 



derived is at least in keeping with what would be expected from 

 svious studies. It will be remembered that T. eucosum and 



T. laciniL.. 



significant 

 Style an 



it is 



pod 



/ 



is short and the stigma small and scarcely, if at all, lobed. No 



characters of taxonomic or phylogenetic importance have been 

 observed here. 



Septum. — The cellular pattern of the septum in this genus is 



very characteristic. Extending nearly or quite from end to end 

 of the pod through the middle of the septum there is a broad 

 region composed of cells elongated parallel to the marginal 



k 



from about one-fou 



half of the surface of the septum and th 



more or less closely compacted. In some species this dense band 

 is yellowish and then it becomes conspicuous even under a 

 hand lens. Such a condition is noticed in T. integrifoliiun and 

 its immediate allies, in T. fiexuosun>, and to a lesser degree in T. 

 crispum. The two marginal bands that occur on either side of 

 the dense middle region often differ in different snecics. The 



short and may be 



elongated 



be irreg 



* ' 



has been 



