Beer, Development of the pollen grain and anther of some Onagraceae. 289 



surrounded by a mucilaginous wall of peciiliar nature. In Epi- 

 lohium tetragoimm tlie primaiy sporogenoiis cells iindergo a Single 

 longitudinal division so that two rows of mother-ceUs are for- 

 med wliilst in Oeuotliera a second longitudinal wall often follows 

 the first so that either two or tree mother-cells are seen in the 

 transverse section of each jjollen sac. The next important step 

 in development is the formation of a mucilaginous wall round 

 each mother-cell. 



This wall is essentiallv similar to that which occurs in a 

 corresponding position in other angiospernis. Mangin^) exa- 

 mined the mother-cell walls of a number of flowering plants 

 and concluded, from their microchemical behaviour, that thev 

 consist of callose in a peculiarly pure State. In Gentiana offici- 

 naÜs and Cainijanida rapuucidoides Mangln^) noted some varia- 

 tious in the composition of the (special -j mother-cell wall. 



From the facts shat this waU, in the Onagraceae, stains 

 deeply with a Solution ef corallin in soda (4:% Na2C03), with 

 aniline blue, benzo-purpurin or congo red, that is gives none of 

 the cellulose reactions wäth lodine reagents and is insoluble in 

 cuprammonia. and that it has no aflinity for ruthenium red. 

 I agree with Mangin in considering callose to be its only con- 

 stituent. 



In several respects, however, I find the reactions of the 

 mother-cell wall to disagi'ee from those usually attributed to 

 callose. Callose is described as readily soluble in 1 ""o caustic 

 potash or soda. I find this Statement to require some modifi- 

 cation with regard to the möther-cell wall. The mother- 

 cell wall of fresh material of Aucuha japonica dissolved 

 with exemplary rapidity in 1 "o caustic soda but I have kept 

 niicrotome sections of material of Oenothera fijced with Flem- 

 niing's Solution for over an hour in 1 % caustic potash and still 

 found the mother-ceUs undissolved at the end of that time. 

 The mother-cell walls of fresh material of 0. hiennis had only 

 disappcared af ter nearly 24 hours in 1 ° 'o Na OH. I have found 

 fresh material of the poUen-mother-cells of the Horse-chestnut 

 equally resistant to 1 % caustic alkali. In 10 "^ o caustic potash 

 the mother-cell walls of Oenothera soon disappear. It will l)e 

 .>;een from these remarks that there is some Variation in the 

 solubility of the mother-cell wall in dilute caustic alkali.<. 



Mangin has affirmed that callose is soluble in phosphoric 

 acid but I have left the mother-cell walls of Oenothera hiennis 

 for many hours in streng phosphoric acid without obtaining any 

 signs of their Solution. Naphtol black, in acid Solution, is said 

 bv Manirin to Stain cellulose but to leave callose uncoloured. 

 I have obtained precisely the opposite result. Bismarck brown, 



1) Mangin, „Observations sur la membrane du Grain de Pollen mur"'. 

 (Bull. Soc. Bot. d. France. T. 36. 1889.) 



-) Mangin, „Observations sur le developpement du polleu". (BuU. 

 Soc. Bot. d. France. T. 30. 1889.) 



