SlB J. LUBBOCH — PIITXOEIOLOGICAL OBSERYATTOJS^S. 317 



ovule Is straight, upriglit, and attached by its base. At the free cud 

 is the " micropyle," aud immediately below it, embedded iu the 

 seed, is a small group of special cells — the rudiment or embryo of 

 the future plant. Now when the pollen falls on the stigma it 

 soon begins to grow. It puslies out a little tube, which rapidly 

 elongates, passes into the cavity of the ovary, enters the micro- 

 pyle or little door, left open, and conveniently placed for it, and 

 vivifies the rudiment of the future plant. 



But ovaries thus constituted are, as I have already mentioned, 

 quite exceptional. Iu a great many plants the seed, instead of 

 being upright and rising at the base of the ovary, is, on the con- 

 trary, attached to the summit and pendent ; and in still more the 

 ovary contains a large number of seeds. Now in a pendent 

 " orthotropous " ovule, the micropyle would be turned away 

 from the pollen-tube ; but the object and effect of the seed 

 being reversed or "anatropous " is to bring the micropyle back 

 into a convenient position. So also, when there are many ovules, 

 the result of the anafropous arrangement is again to bring the 

 micropyle into a suitable position. 



The structure and arrangement of the ovule have been the 

 subject of various important memoirs, which, however, have been 



almost exclusively descriptive.- Dalmer * indeed quotes Schleiden, 

 ^vho, speaking of Berhcris, pointed out that among the normal 

 anatropous ovules here and there one occurs which is ortho- 

 tropous, and that these never develop into seeds (" Die Befruch- 

 tung der Ovule scheint mir aher inganz bestimmlerBeziehung 

 zu dem vorgeschriebenen Lauf der Pollenschlauche zu stehen, 

 deun slets beobachtetc ich, dass diese regelvvidrigo atropen 

 Eiclien unbefruchtet blieben "). The pollen-tubes, however, 

 would naturally follow the regular course; and we could not, 

 I think, deduce a general conclusion from such rare and 

 abnormal cas-es. Dalmer himself docs not seem to have dune 

 so ; for, after referring to the diflerent forms of seeds, he ob- 

 serves that '^sometimes the form of the ovule appears to be 

 adapted so as to facilitate the entrance of the pollen-tube" 

 C^ scheint zuweilen die Geslalfc des Ovulums dem Eintritt des Pol- 

 lenschlauches angepasst zu sein"). Even here, then, the expla- 

 nation I venture to suggest seems referred to rather as an excep- 

 tional occurrence than as a general explanation of this remarkable 



** Ueber die Leitung der rollenschlauche bei den Angiosperuien," Jeiiaiscli, 

 Zeils. 1880, p. 530. 



