1836.] Some remarks on the development of Pollen. 733 



and in all were separable by slight pressure. Each of these divisions 

 is at this period a young grain of Pollen. On making their escape 

 they leave their proper cells attached to the interior of the parent cell, 

 which is hence divided into as many cells as there are divisions of 

 the nucleus. The young grains are oblong-ovate, flattened on their 

 contiguous or inner faces, and open along the centre throughout the 

 whole length of their outer faces. They are even at this period reti- 

 culate, and have rather a papillose appearance ; they are lined by an 

 inner membrane in the form of a hyaline sac which bulges out 

 slightly along the opening just mentioned. 



When the perianth is three lines long, the grains of Pollen have 

 undergone complete separation ; no traces of their original envelopes 

 being visible. They vary much in size, are rather opaque, minutely 

 reticulate, and marked along one side by a longitudinal semi-trans- 

 parent line, which indicates the situation of the original opening, now 

 closed up by the inflection of its edges. Immersion in water produces 

 scarcely any action on them. At a later period, the perianth measuring 

 five lines in length, the grains are considerably increased in size. Im- 

 mersion in water causes the inflected margins of the furrow to secede, 

 until they become widely separate. Through this the inner membrane 

 bulges out to a considerable extent. 



Perianth about six lines in length : the Pollen is now perfectly 

 formed ; the grains vary much in size, the smaller being probably 

 abortive, but theya 11 undergo the same changes on immersion in 

 water. This causes the outer coat to be pushed back by the expan- 

 sion of the inner, which is now nearly filled with minute granular 

 matter. 



At the time of dehiscence of the anthers the grains vary much in 

 size : the more perfect are lanceolate in outline, of an orange colour, 

 distinctly reticulate or cellular, and open on one side along the centre. 

 This, however, is perhaps to be attributed to the excessive moisture of 

 the climate. Immersion in water causes the very rapid bulging out 

 of the inner membrane, which pushes back, and at length nearly en- 

 tirely off, the outer one. This is filled with minute granular matter, 

 the fovilla and burst of the immersion is somewhat protracted. 



Stigmatic action causes the production of a tube or boyau from the 

 inner membrane, the head of which tube continues to be covered 

 partially by the outer coat. 



This instance is interesting as an example of the development of 

 Pollen by the division of an originally simple nucleus and of perfect 

 and almost spontaneous separation of the outer coat, and lastly as 

 5 c 



