504 Prof. Dow's Descriptions of Indian Gentianez. 
Although the Gentianee undoubtedly constitute a very natural family,- 
agreeing remarkably in their habit and structure, and also in their sensible 
properties, they afford very few absolute marks to distinguish them from the 
other families to which they are related. When taken in an extended sense, 
the Gentianec may be said to hold an intermediate station between Apocynec 
and Rubiacee, differing from the former, to which they are more intimately 
allied, in the larger quantity of albumen, and in the much greater develop- 
ment of their embryo; from the latter in their free ovarium, and from both 
by their persistent corolla, and in the nervation of their leaves. We may 
compare Crawfurdia with Gelsemium, of which it possesses the twining habit 
and most of the characters, but the latter is essentially distinguished by its 
penninerved leaves, deciduous corolla, and concrete carpels, which unite it to 
Apocynee. Some species of Lisianthus resemble Allamanda in their woody stem 
and in the structure of their flower, and the twisted æstivation of Apocynee 
occurs also in Erythrea and Gentiana contorta. There is an evident affinity 
between the Rubiaceous genus Oldenlandia and Mitrasacme, which also ac- 
cords in many respects with Spigelia and Mitreola, but it differs in the imbricate 
zestivation of its corolla. Seeing, however, the near approach to the valvate 
form of æstivation in Slevogtia, and that Spigelia and Mitreola agree with 
Gentianee in habit, I am led to question the propriety of considering them 
in any other light than as forming a subordinate group of that family. The 
genus Canscora, by its irregular flowers, and by its resemblance in habit to 
certain Gratiolec, especially to Torenia, would seem to establish a relation- 
Ship between the Scrophularinee and this family. 
The essential characters of Gentianec consist in their persistent usually 
plicate corolla; in the two carpels composing the pericarpium being placed 
right and left with respect to the axis of the flower; and lastly, in the nerva- 
tion of their leaves, which bears a considerable resemblance to that of Mono- 
cotyledonous plants. "These characters only apply to the normal Gentianee, 
and necessarily exclude the three small groups of Spigeliacew, Loganiacece, and 
Potaliacew, which Dr. von Martius has proposed to separate from them. In all 
these, however, the relation of the carpels to the axis of the flower is the same 
as in Gentianec, but they have all a deciduous corolla, and in the last two 
the leaves are penninerved. Another group, the Menyanthee, consisting of 
