REPORT ON THE PHILOSOPHY OF BOTANY. 4<3 



the stomata of Marchantia are in some respects different from 

 what are found upon flowering plants ; yet I think we can hardly 

 doubt that the plan upon which they are all formed is essen- 

 tially the same. 



Dutrochet also confirms * the statement of Amici, that the 

 stomata are perforations ; for he finds that when leaves are de- 

 prived of their air by the air-pump, it is chiefly on the under 

 side, where the greatest number of stomata is found, that little 

 air bubbles make their appearance ; and that it is through the 

 stomata that water rushes into the cavernous parenchyma to 

 supply the loss occasioned by the abstraction of air. 



Anther, ^c. — Some curious remarks upon the nature of the 

 tissue that lines the cells of the anther have been published by 

 Dr. John E. Purkinje, Professor of Medicine at Breslau. His 

 researches are chiefly directed to the determination of the na- 

 ture of the tissue that is in immediate contact with the pollen; 

 and he has demonstrated in an elaborate Essay f, that the opi- 

 nion emitted by Mirbel in 1808 ;{:, that the cause of the dehis- 

 cence of the anther is its lining, consisting of cellular tissue cut 

 into slits and eminently hygrometrical, is substantially true. 

 He shows that this lining is composed of cellular tissue chiefly 

 of the fibrous kind, which forms an infinite multitude of little 

 springs, that when dry contract and pull back the valves of the 

 anthers by a powerful accumulation of forces which are indivi- 

 dually scarcely appreciable : so that the opening of the anther 

 is not a mere act of chance, but the admirably contrived result 

 of the maturity of the pollen, — an epoch at which the surround- 

 ing tissue is necessarily exhausted of its fluid by the force of 

 endosmosis exercised by each particular grain of pollen. 



That this exhaustion of the circumambient tissue by the en- 

 dosmosis of the pollen is not a mere hypothesis, has been 

 shown by Mirbel in a continuation of the beautiful memoir I 

 have already so often referred to §. He finds that, on the one 

 hand, a great abundance of fluid is directed into the utricles, 

 in which the pollen is developed a little before the maturity of 

 the latter, and that by a dislocation of those utricles the pollen 

 loses all organic connexion with the lining of the anther; and 

 that, on the other hand, these utricles are dried up, lacerated, 

 and disorganized, at the time when the pollen has acquired its 

 full development. 



* Annales des Scie?ices, vol. xxv. p. 247, 



t De CelluUs Antherarum fihronx. 4to. Wratislaviae, 1830. 



X " Observations sur un Systeme d'Anatoniie Comparee de V^getatix, foiides 

 sur rOrganization de la Fleiir," in Memoires de l' List Hut, 1808, p. 331. 



§ "Complement des Observations sur le Marchantia poli/vwrpha," in Ar- 

 chives de Botanique, vol. i. 



