70 LETTER IV. 



notion of the essential characters of any of the tribes, 

 but it states clearly how they differ from each other. 

 They differ from each other in many other respects, 

 bat it was not necessary to express any thing further 

 in order to enable you to know them from each other. 



EXPLANATION OF PLATE IV. 



I. The Cruciferous Tribe. — A sprig of Shepherd's Purse. — 

 1 . A flower with all its parts in their natural position. — 2. The same 

 flower without the calyx and coroUa ; it shews the two side stamens, 

 which are the shortest.— 3. An ovary cut across, exposing the par- 

 tition, the two cavities and the young seeds, or ovixles. — 4. An ovule 

 apart, with the end by which it hangs from the side of the partition. 

 .5. The stigma, with the style and a portion of the shoulders of the 

 ovary. — 6. A ripe sihcle ; a a the valves; h the point of the par- 

 tition. — 7. The partition, from which the valves have been removed, 

 shewing the numerous seeds which hang to it. — 8. The partition seen 

 in front, with the marks of the places to which the seeds were 

 attached. — 9. A ripe seed, covered with fine hairs. — 10. The same 

 cut through perpendicularly, shewing how the embryo is doubled up 

 within it. — 11. The same seed, cut through horizontally; a the 

 radicle ; b the two cotyledons. — 12. An embryo pulled out of the 

 seed-coat and straightened. 



II. The Violet Tribe. — A. A piece of Heartsease ; a blade of 

 the leaf ; b b stipules. — 1. A view of the stamens and pistil in their 

 natural position, after the petals and sepals are pulled off. — 2. One 

 of the horned stamens seen in face ; and, 3. the same seen from 

 behind ; in both a represents the membrane, which is characteristic 

 of the natural order. — 4. A regular anther, seen in face. — 5. A 

 pistil. — 6. Tlie ovary cut through to exliibit the tliree elevated Unes 

 on which the seeds are placed. — 7. A front view of the hole that 

 leads to the stigma. — 8. The head of the stigma spht open, with a 

 view of the stigmatic interior. — 9. A ripe fruit split into its three 

 valves. — 10. A seed. — 1 1. The same cut perpendicularly to shew the 

 embryo lying in the midst of albumen. 



