65 



form, and that is nearly related with the one from Mexico, described 

 as W. gladiata. As is correctly observed in your description, the 

 Florida is distinguished from the Mexican plant by the much (13-2 

 times'* greater elongation of the fronds. The apical portion especially 

 is considerably narrower in proportion ; and, although there is always a 

 part of that portion destitute of air-cavities, yet that part is relatively 

 shorter. Moreover, the sabre-like curvature of the fronds is often 

 more decided. The last two characters are directly associated with 

 the more elongated forms. I have some doubts, however, whether it is 

 advisable to distinguish W. Floridana as a species. From my observa- 

 tions of other Lemnaceae I should hardly venture to found a sepa- 

 rate species upon the above differences. At any rate, however, we 

 have here a beautiful and interesting form, the discovery of which m 

 such quantities in Florida constitutes an important contribution to 

 the Flora of the United States. Had both forms come to my knowl- 

 edge at the same time, I should probably have taken the Florida 

 plant for the type of the species, inasmuch as it is constant with 

 itself wherever you have found it ; and the Mexican plant would 

 have been treated as a var. abbreviata. The Cedar Keys specimens 

 are the best adapted for study of structure, as they abound m_ starch, 

 and after colorization by chloride of zinc the extent to which air- 

 cavities prevail becomes plain." 



Wolffielh 



These 



W. 



ulata, Heglm., from South Africa, has air-cavities embracing the 

 whole frond and the pouch, but pigment-cells are not present at the 

 anterior end, and the apex of the linear frond is truncate and den- 

 ticulate. In W. oblonga, Philippi, from Chili, and in W. lingulata, 

 Hegelm., from Mexico, Brazil and India, pigment-cells pervade the 

 whole plant, air-cavities embracing in the former species every part 

 except the pouch, and in the latter species only a small part of the 

 posterior end of the frond ; the outlines of each are as indicated by 

 their names. I am indebted to Messrs. Sereno Watson and Charles 

 F. Parker for the opportunity to examine typical specimens of W. 



ladiata and W. lingulata. . . 



But Dr. Hegelmaier has remarked upon two singular deviations, 

 which all of these plants exhibit from the type of Wolffia, and 

 which have led him to conjecture that Wolffiella will constitute a 

 distinct genus when its reproductive organs shall come to be known. 



ist. The insertion of the' stipe at the basal angle, and the posi- 

 tion of the costa along the lateral margin of the pouch, cause the 

 frond to be transverse, instead of median, zygomorphous. 



2d. The stipe and costa of the cohering young frond occupy the 

 opposite side of the pouch to those organs in the parent frond.- 

 Hence, if we detach the two fronds from each other, and bring them 

 into superposition without changing their exposed surfaces, they will 

 be found to have stipe and costa similarly right and left, and their 

 agreement to be absolute, and not relative as in a pair of opposite 

 leaves. This anomaly has been found difficult to interpret morplio- 

 logically in the absence of any knowledge of the inflorescence ot 

 these pfants. John Donnell Smith. 



Baltimore, Mav 2iiJu 



