1909] Bartlett, — On Oxalis stricta var. viridiflora 119 
а cap on the tip of the lengthening fruit. At the type station of Oxalis 
stricta var. viridiflora Mr. Hus found only a few individuals. ‘The 
occurrence of the plant in greater abundance at a distant locality 
strongly confirms its worth as a systematic variety. Although it has 
doubtless had an independent origin at different places, its characters 
are definite and show no greater range of individual variation than do 
those of typical Oxalis stricta. 
The green petals resemble sepals in the presence of chlorophyll in 
the sub-epidermal tissue and in the increase in number of stomata 
and hairs. They differ not only from sepals but also from typical 
yellow petals in the shape of the epidermal cells, which are prevailingly 
isodiametric instead of narrowly oblong. ‘The breadth of the petals 
may be correlated with this character of the epidermal cells. Results 
of hybridization experiments with typical Oxalis stricta and var. 
viridiflora will be looked forward to with interest, since it is difficult 
to see, if it be true, as Mr. Hus believes, that var. viridiflora is a varia- 
tion differing in only one essential character from the parent species, 
just how the modified shape of the epidermal cells can be interpreted 
as a consequence of the presence of chlorophyll, or vice versa. It is 
not as though the variation were true sepalody, for in that case the 
development of two instead of one whorl of sepals might be a unit 
character, which would be exclusive with regard to the development 
of petals. 
According to Dr. Small’s treatment of the species of Yantho.alis,! 
certain species are classed into two groups, depending upon whether 
the longer filaments are glabrous or pubescent. Oxalis stricta falls 
in the group with glabrous filaments. Although this character does 
not hold perfectly in the material from Thomson, there is a sufficient 
difference in degree of pubescence so that a species like Oxalis filipes, 
which belongs to the group with pubescent filaments, can be very 
readily distinguished from Oxalis stricta. In var. viridiflora, however, 
the filaments are fully as pubescent as those of Oxalis filipes. If 
there should be found variations of other species of Oxalis parallel to 
Oxalis stricta var. viridiflora, this fact ought to be allowed for if the 
attempt is made to place them by means of Small's key. 
CAMBRIDGE, MASSACHUSETTS. 
1 N, Am, Fl. xxvi. (1907) 50. 
