176 Meyen^^ Report for 1839 on Physiological Botany. 



different in various families. I here refer to what I have ob- 

 served of its formation in Mais, 



In the Botanical Society of Edinburgh* Mr. Giraud read 

 a treatise on the structure and function of the pollen, from 

 which it appears that he has arrived at the same results as 

 have been published in the modern German works on this sub- 

 ject. In Crocus vernus Mr. Giraud saw three pollen tunics; 

 and on the surface of the pollen grains of Polemonium coeru- 

 leum he found small opake particles, which exhibited a pecu- 

 liar motion as soon as put into water. The grooves which are 

 found on some spherical and ellipsoidal pollen grains do not 

 appear to Mr. Giraud to be clefts in the outer membrane. 

 The chemical examination of pollen showed the presence of 

 potash in the pollen of Antirrhinum majus, as also of acicular 

 crystals of phosphate of lime, etc., etc. Mr. Giraud found also 

 that warmth assists the formation of the pollen-tubes. 



In the ^Botanical Register^ t is a note on the appearance of 

 amylum on the surface of the pollen grains of Polemonium 

 coeruleum, the formation of which is derived from the primi- 

 tive cells (Mutterzellen). [The presence of amylum, if it be 

 really true, can only be considered as an exception to the rule 

 and as unimportant, for it is by no means general. — Meyen.'] 



At the meeting of Naturalists at Freiburg M. A. Braun J 

 made known his observations on the arrangement in the burst- 

 ing of the anthers; he proved that the order in which the an- 

 thers open agrees only in few cases with the genetic succes- 

 sion of the stamina, indeed is sometimes just the contrary; 

 but in most cases where a real succession takes place, it 

 stands in no relation to the genesis. From a great number of 

 observations M. Braun draws the following cases, in which 

 the order of the opening of the anthers appears : — 



I. Simultaneous opening of all the anthers. II. Cyclous- 

 successive opening, and either in centripetal or centrifugal 

 succession. III. One after the other (gliederweisej successive 

 opening; this takes place, 1. in spiral succession, {a.) centri- 

 petal or progressive, {b.) centrifugal or regressive, (c.) from the 

 central region, passing either forwards or backwards, and {d.) 

 in a determinate spiral, etc., or, 2. the opening does not take 

 place in spiral succession. Here it passes regularly from one 

 side of the flower to the other, or in an apparently irregular 

 but still constant succession. 



By a communication in M. MussehPs ^ Praktischem Woch- 



♦ Annals of Natural History, April 1839, p. 127. 



t 1839, p. 52. J Flora von 1839, p. 302. 



