EXPLANATION OF THE PLATES. 277 



Plate III. — Embryogeny in Phanerogamic Plantb. 



Figs. 1-4 (from Hofmeister) illustrate the process in the Coni- 

 ferae (pp. 57, 183). 



Fig. 1. — A section of the naked ovule of Pimis sylvestrie in 

 the spring of the year after impregnation. In the niicropyle at 

 c are seen two poUen grains, with theii* tubes turned in the direc- 

 tion of the internal cellular mass b, going under the name of 

 the alhumhwus body, and corresi)onding to the prothallium of 

 the higher Cryptogamia. 



Fig. 2. — Part of a similar section of the ovule of Pinus 

 Strobios, in early summer ; a upper part of the nucleus, which 

 the pollen-tube, after a long period of inaction, has now netirly 

 traversed, in its way to impinge on the wall of the albuminous 

 body b, immediately over one of the clusters of flask-shaped 

 cavities or corpuscula d, which have just been formed in tliat 

 body, and which seem to correspond to the archegonia of the 

 higher Cryptogamia on the one hand, and to the embryo-sacs of 

 the majority of the Phanerogamia on the other. 



Fig. 3. — A magnified view of a corpusculum of Pinus ^ijlvts- 

 tiis, showing at e the germinal particle which is developed into 

 the embryonic structures on impregnation, and, at ti, two of 

 the four cells which represent the canal of the archegonium — b 

 tissue of the nucleus, c cellular contents of the corpusculum. 



Fig. 4 illustrates the result of impregnation, in the formation 

 of a cluster of four pro-embryos, three of which have been cut 

 away near the base ; b proper embryo formed by a new process 

 of cell formation at the lower extremity of the suspensor o. 

 (Pinus Strobus). 



Figs. 5-8 illustrate the same process in the Angiospernions 

 Phanerogamia — (p. 61). 



Fig. 5 (from Schleiden) shows the emission of tubules by tlie 

 pollen grains, and their penetration through the conducting cel- 

 lular tissue of the style. 



Fig. 6.— Section of an ovule of Polygonum divaricaiumy (from 

 Schieiden) showing the seed-coats, the micropyle c, and the 

 nucleus a, with its large embryo-sac 6. 



FicT. 7.— Ovule of CEnotli^ra (from Hofmeister), showing 



