266 Dr. Dickie on the Ovule of Euphrasia officinalis. 



Graminece. Its independence of the pollen need scarcely be 

 spoken of in Cazlehogync and Citrus already alluded to. The ob- 

 servations of Mohl on the Orchidea lead to the same conclusion ; 

 those of Miiller on the same family have a similar import. Mr. 

 Henfrey in his report already quoted obserVes, " The whole 

 question appears to be narrowed to the determination of the 

 point, whether the germinal vesicle does actually exist before im- 

 pregnation, since if that can be proved, all appearances yet ob- 

 served may be reconciled by allowing for very slight errors in 

 interpreting and delineating them." 



The most careful and trustworthy observers speak with caution 

 respecting the real nature of the action produced by the pollen- 

 tube upon the ovule in impregnation. We have seen that at 

 least one stage of embryo-life is independent of the contact of the 

 pollen-tube with the embryo-sac ; this I have ventured to deno- 

 minate the sporoid stage. In some few cases, viz. Ccelebogyne and 

 others, all the stages are equally so; generally however the 

 future progress of the embryo is determined by the action of the 

 pollen, whatever the nature of that action may be. The pro- 

 duction of true radicle, cotyledons and plumule will constitute 

 the last stage of embryo-development, and it is in reference to it 

 that the best instruments cease to afford us any precise informa- 

 tion. We can trace the progress of the organs in question, but 

 we cannot state precisely in what way the action of the pollen 

 influences their development. We do not derive any very clear 

 information from such statements as those of Oken*, when he 

 tells us that " the pollen electrifies, animates or inspirits the 

 ovarium — that the male imparts nothing in impregnation but 

 the solar ray or fluid nervous mass in its semen, which awakes, 

 animates and inspirits the quiescent female — that the pollen is 

 a most highly differenced electrical product ; the seed-granule a 

 wholly indifferent and tranquil mucous mass. The pollen falls 

 upon the stigma of the pistil, and irradiation has taken place ; 

 the material fruit- capsule gains thereby so much polarity, that 

 saps enough ascend, in order to develope the germless seed- 

 vesicles." 



The theory of Schleiden had the advantage over all others that 

 it directly accounted for the presence of the embryo. Some ob- 

 servations of Mr. Griffith seemed to lead to a conclusion nearly 

 similar, the difference being that the embryo is not developed 

 directly from the end of the pollen-tube, but from cells produced 

 by that part. It is presumed that no one has hitherto traced a 

 tube through its whole length, connected with the pollen-grain 

 at one end and with the embryo at the other. 



* Oken's Philosophy of Nature, Ray Society, 1817. 



