EXPLANATIONS OF THE PLATES. 597 



j. 2. Longitudinal section of the same. The letters indicate the same 

 sepals. An epithelium distinct from the parenchyma can be clearly seen. 



Fig. 3. A later condition. The sepals have already the commencement of the 

 wing-shaped keel upon their backs. The foundations of the bud are perfectly 

 developed. 



Fig. 4. Longitudinal section of the same. The same letters designate the same 

 sepals. Between the two there is a leaf of the corolla, and in front of b another 

 cut through. Right and left of the corolla-leaf, in the middle, are two little ele- 

 vations, which are the commencement of stamens cut through. 



Fig. 5. A somewhat late condition (the bud with the bracteola, about l mil- 

 limeter long) : the three calyx-leaves (sepals) alternate with the two corolla- 

 leaves (petals), and between these there is a little elevation, which is the first 

 appearance of a stamen-leaf (stamen). The two last figures are somewhat 

 smaller than half, so that the wart-like termination of the axis in the centre is 

 not seen. 



Fig. 6. A later condition. The five sepals are distinct. The petals are seen 

 alternating with them, and the stamen with these. In the centre the axis is 

 conspicuous as the germen (cauligenum) with a cavity, but as yet no trace of a 

 style (carpellary leaf). 



Fig. 7. Longitudinal section, later still. The whole flower is perfectly deve- 

 loped, a, Longitudinal section of sepal ; a', a second, seen from the edge ; 

 6, petal ; a and b are attached to a cyathiform extension of the axis f, (a disc) j 

 c, section of stamens ; d, another from the side ; e, pistil. 



Fig. 8. The pistil at the same stage of development, seen from above. Three 

 carpellary leaves are seen at the edges of the germen. 



Fig. 9. Outline of a transverse section of a corolla, directly above the pistil. 

 The petals still exhibit the valvate condition of the bud. In the three last tissues, 

 where all the leaf-organs are formed, from the calyx to the carpellary leaves, there 

 is not the slightest trace upon the disc of the presence of the corona. It cannot, 

 therefore, be formed from the foliar organs. 



Fig. 10. A longitudinal section in a yet later condition, a, Sepal ; b', petal 

 seen from the edge ; c, stamen cut through ; c', lower part of the germen and 

 disc f, upon which, at g, the various forms of the corona begin to be developed 

 as mere cellular (hair-like) growths. 



Fig. 11. An almost complete longitudinal section of the entire flower, at a 

 yet later period, a, Sepal (lower half) cut through near the wing-shaped keel ; 

 of sepal seen from the edge ; b, petal ; b', another seen from the edge ; c, lateral 

 view of a stamen ; c' ', lower part of a stamen cut through ; d, germen (germen cau- 

 ligenum) cut through : on both sides the commencement of the seed-bulbs project 

 into the cavity ; e, style (carpellary leaf), with a lateral view of the stigma ; e' ano- 

 ther, with the canal exposed ; /, enlargement of the axis between the calyx and 

 petals (disc) ; g, continuation of the axis above the petals (filaments) ; h, continu- 

 ation of the stamens (gynophore) ; i, corona. 



Figs. 12 18. Development of the Anthers. 



Fig. 12. Transverse section of anthers of fig. 7.: a, groups of strongly thick- 

 ened cells ; b y foundation of vascular bundles ; c, foundation of four anther- 

 valves. 



Fig. 13. Transverse section of part of an anther-cell, at a period between 

 figs. 7. and 10. a. Epithelium, b. Developing cellular tissue with great cytoblasts, 

 out of which at a later period the various layers of anther-valves are developed. 

 c. Primitive parent-cells, with great parietal cytoblast for the formation of pollen. 

 After these cells are perfectly formed and arranged by the formation of cell 

 within cell, there originates in every cell an individual cell which is perfectly and 

 easily separable, and these remain isolated when the first are dissolved up. In 

 the isolated cells (parent-cells of Niigeli ; they might be called special parent-cells) 

 are formed four free cytoblasts, and around these are formed four free cells. 



Fig. 14 exhibits the last condition. A. A parent-cell in which are two 

 active (pollen) cells and a cytoblast : the fourth lies on the other side, and is not 

 seen. J3. An individual pollen-cell separated from another parent-cell of the 



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