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and lastly the Glumaceous. How far these five groups are strengthened by variations in the conformation of seed, I am as yet unable to say, not having given that attention to the subject which it requires, but I apprehend when they also are closely examined, with special reference to this enquiry, that many points in confirmation of their stability will be found and, with their aid, a series of perfect circles be discovered presenting striking analogies with others referable to the exogenous circle. Until however this is effected Lindley's very practical, I think also most natural distribution of these tribes, leaves little to be desired by the practical botanist.
On the last great division of the vegetable kingdom the Acrogens or Cryp- togamic plants I have nothing to add to what I have already said. This group certainly forms the aberrant circle, and like the analogous circles in the animal kingdom is made up of three smaller ones, each of which seems complete, though all require verification.
For those wishing to acquire a deeper insight into the science of plants than these pages can possibly supply, I would particularly recommend the study of Dr. Lindley's Elementary Botanical works which are by far the best in the English language. His recently published Vegetable Kingdom I have not yet seen, but it is very highly spoken of by two of my Correspondents who have. In its arrangement, I learn, he has considerably departed from both those referred to above, as given in his Elements and Natural System, falling back in a great measure on the plan of Jussieu, but greatly improved. To those desirous of be- coming acquainted with the first principles, and many of the details of the cir- cular system of classification, Swainson's volumes of Lardner's Cyclopædia are the only easily procurable text books and are among the most interesting volumes I ever read on Natural History.
