400 Mr. H. Giraud on some peculiarities in 



nor granules are emitted, but this outer membrane gradually 

 removes from off the grain, M'hich still retains its original 

 figure, and incloses its contents as perfectly as ever. Instances 

 of this kind of action are represented in Plate XVIII. Fig. 1. 

 shows the pollen of Fritillaria meleagris with part of its outer 

 tunic removed. Fig. 2. the pollen-grain wholly denuded of 

 its outer tunic. Fig. 3. a portion of the outer tunic removed. 

 Fig. 4. the pollen of Lilium Mart agon, its outer tunic thin and 

 transparent, rent and falling off. By employing this method, 

 I have succeeded in detecting a third tunic in the pollen of 

 Crocus vernus. When immersed in diluted sulphuric acid 

 the pollen-grain swells (fig. 5.), its outer tunic bursts and is 

 deciduous, as is represented at fig. 6. At this stage the next 

 tunic, thin and transparent, may be clearly defined ; but after 

 a short interval, it expands, exposing within it a third tunic, 

 which incloses the pollenic granules and fovilla (fig. *J.). 



In examining the pollen oi Polemonium cosruleum, immersed 

 in water, with a poMer of about 500, the surface of the grains 

 appeared studded with very minute and perfectly opake 

 bodies, some of which left the grain, and floated in the water 

 on the object-glass (fig. 8. a.). Upon looking more atten- 

 tively at these bodies, I found that each possessed a sponta- 

 neous and independent motion, exactly similar to that pos- 

 sessed by the globules of the blood, or to that which Brong- 

 niart describes as having witnessed in the granules of the pol- 

 len of the Gourd and of the Mallow. Although I could de- 

 tect no grains that had burst, still I supposed that these 

 bodies might be the pollen granules, and that therefore this 

 was merely a repetition of the observation of Brongniart. The 

 pollen-grains being made to burst and emit their granules, 

 an obvious distinction at once, between the latter and the 

 minute bodies, became apparent. The true granules were 

 larger than these bodies, from which they might also be di- 

 stinguished by their translucency. Of the nature or uses of 

 these bodies I have not been able to form even a conjecture ; 

 but that their motion is independent of all external agencies 

 I feel quite satisfied. 



Considerable doubt has existed as to the true nature of the 

 longitudinal line which exists in most elliptical and spherical 



