375 



BOOK, IV. 



Chapter, 2. On the Sexual Organs of Gymnosperms, and relatwe 

 value of Characters in Botanical Classification. 



Podocarpus or Taxus. The pollen of this, (which is named in my 

 Bootan List no. 529) Abies Brunonis, is simple and angular. Immer- 

 sion in water causes it to become circular, the discoid centre and the 

 external margin being opaque, it is brownish, and the disc is as usual 

 granular. After some time, immersion causes the centre to protrude, 

 apparently at no definite point, and this protrusion is soon carried so 

 far, that the outer coat is thrown off, frequently too with a jerk. 

 The centre now appears as a gelatinous hyaline mass, with a gra- 

 nular disc. This hyaline portion, is evidently extensible, and after 

 protracted immersion assumes irregular forms. I have not seen any 

 protrusion of a boyau, or any alteration in the granular disc. 



Spirits of wine causes the pollen to contract, but renders it the 

 more transparent : immersed in this fluid it appears angular with a 

 central striate granuliferous portion of nearly equal extent with the 

 outer coat. Subsequent immension in water causes it to undergo 

 the same changes as simple immersion in water, but the central 

 granular disc always remains contracted. The last circumstance 

 to be noted, is the appearance of an inner disc surrounding the gra- 

 nular mass. 



It is this areola round the centre, that induces me to believe M. 

 Mohl's assertion respecting the three coats to be correct. The fovilla 

 must be of a singular nature, since the mobility of the fovillam of 

 many (most ?) pollens continues active in spirit of wine, while in this 

 they become aggregated into an irregular grumons mass. 



Nothing can prove more distinctly the nature of the outer coat of 

 pollen than this instance, because it is unprovided either with fold 

 or pores, it is thrown off by bursting. 



The extensibility of the hyaline coat would seem to militate 

 against Mohl's opinion, because it is the coat in contact with, or en- 

 closing the fertilising particles that is extensible, and yet the*want of 

 change of form of the granular disc, in conformity with that of the 

 hyaline coat strengthens it. But this will be cleared up by ob- 

 serving the effect of scigmatic action. 



