47 
genus. Notwithstandimg these exceptions, the species for the 
present must be referred to Avicu/aria and forms the first excep- 
tion to its normal morphology as far as I have observed, and an 
interesting one. 
Explanation of Plate 293. 
- Whole plant, natural size, 
- Leaf, enlarged. 
- Flower, enlarged. 
. A stamen, enlarged, 
- Achene, enlarged. 
. Cross-section of achene, enlarged. 
Aun & wb 
The Relation between the Genera Thysanella and Polygenella as shown 
by a hitherto unobserved Character. 
By Joun K. SMALL, 
The genus Thysanella has generally, and apparently without 
g00d reason, been included in Polygonum. 
In a former paper * I stated that Zhysanella was a perfectly 
distinct genus, related to Polygonella and not to Polygonum. 
A glance at ThysaneHa fimbriataand any member of the genus 
Polygonella ought to be sufficient to convince any one of the strong 
relationship between the two genera. The habits of the two are 
almost identical, while the vegetative organs of 7/ysanellamuch 
more closely resemble those of Polygonella than they do or 2 
member of Polygonum. ; 
Oming to special morphological characters let us gn es Toes 
Sider the flower. Here we find the special development in eh 
inner series of sepals ; likewise in Polygonella it is the inner we 
that develop special organs. In Polygonum the outer sepal 
. :; ies ee ; - 
Specialized if any development at all takes place, the inner seri 
being practical odified ee 
y unmodified. | re 
Besides the foregoing considerations I have a 
character in both the genera Thysanella and day Sneied ‘me 
Possessed by no other member of the family Polygonac open 
_ *Mem, Dept. Bot. Col. Coll. ihr cua 
