EXPLANATIONS OF THE PLATES. 599 



Figs. 4 6. Formation of the Stigma. 



Fig. 4. , Style ; b, stigma, slightly magnified. 



Fig. 5. Longitudinal section of part of the style and stigma, a, Epidermis ; 

 b, parenchyma ; c, canal of the style, in which is continued the delicate gelatinous 

 parenchyma of the stigma as a conducting cellular tissue ; d, papilla of the 

 stigma. 



Fig. 6. An individual stigmatic papilla, strongly magnified, terminating in two 

 papillary cells (a), between which eventually the pollen-tube penetrates. 



Development of the Embryo. 



Figs. 7 9. Epilobium hirsutum. 



Fig. 7. A small portion of the stigma. , Pollen-grain with detached fibres (b) 

 and two pollen tubes (c), of which the left has already penetrated through the 

 papillae (d) to the parenchyma (e) of the stigma. 



Fig. 8. a, The seed-bud and a portion of the conducting cellular tissue (e) of 

 the germen. The pollen-tubes (d d) are passing down the conducting cellular 

 tissue, and one of them enters the foramen (b) of the seed-bud (ovule) ; c, hairs 

 of the seed-bud at its base. 



Fig. 9. Longitudinal section through the foregoing seed-bud, a, Papillary 

 epidermis; b, parenchyma of the external envelopes of the bud; c, internal enve- 

 lope ; d, nucleus ; e, raphe ; /, tuft of hair at the base of the seed-bud ; g, pollen- 

 tube entering the foramen ; h, sac of the embryo. 



Figs. 10. and 11. Orchis Mono. 



Fig. 10. Soon after the entrance of the pollen-tube. a y Inner integument: 

 b, sac of the embryo, which has perfectly supplanted the nucleus ; c, pollen-tube. 



Fig. 11. Prepared free from the seed-bud, a, The pollen-tube, which clearly 

 as a continuous membrane surrounds the cells which are contained in it, and of 

 which (6) forms the embryo ; c, the peduncle of the embryo (embryotrager), which 

 at a later period projects from the seed-bud. 



PLATE VI. 



Development of the Embryo continued. 

 Figs. 1. and 2. Orchis latifolia. 



Fig. 1. Longitudinal section of a seed-bud, a, External integument ; b, inter- 

 nal integument ; c, d, two pollen-tubes, whose penetrating extremities have formed 

 the foundation of two embryos. 



Fig. 2. Longitudinal section of the lower part of a seed-bud, a d, As in fig. 1. 

 The pollen-tube, c, has penetrated the right spot and has developed a perfect 

 embryo ; but the other, d, has missed the inner foramen and passed between the 

 internal and external integument, and in this case has formed a rudimentary embryo. 



Figs. 3. and 4. Salvia bicolor. 



Fig. 3. Longitudinal section through the seed-bud, a, Epidermis of the simple 

 integument (&) ; c, the epidermis of the supplanted nucleus (inembrana nuclei, 

 Rob. Brown) ; d, raphe ; e, the sac of the embryo, which has extended itself above 

 the nucleus into the canal of the foramen of the seed-bud ; f, pollen-tube pene- 

 trating into the embryo-sac, where it lays the foundations of the embryo. 



Fig. 4. Pollen-tube prepared from the foregoing, a, The under, looser part 

 dilated (with the extension of the embryo-sac) ; c, upper portion attenuated and 

 filled with some cells which subsequently form the peduncle of the embryo ; b, 

 large globular cell developed at the extremity of the pollen-tube, and which is 

 the basis of the embryo. 



Q Q 4 



