138 Miscellaneous. 



On the Structure of the Anthers in the Aroidese. 



By M. VAN TiEGHEM. 



From his investigations Chatin has deduced the general rule, that 

 anthers which open by terminal pores are destitute of fibrous cells. 

 The genus Solanum, the anthers of which have fibrous cells round 

 the terminal pore, forms a curious exception to this. The author 

 indicates the occurrence of similar exceptions in the apicilar anthers 

 of several Aroidece. 



The sessile anther of Richardia africana, Schott, has two loculi, 

 each divided into two locelli by a delicate longitudinal septum ; and 

 these open at the apex by a small vertical tube pierced through the 

 thick plate formed by the connective above the loculi ; beneath this 

 terminal pore the septum is absorbed, to enable the loculi to com- 

 municate. The inner wall of the chamber is clothed, when mature, 

 with a layer of prismatic cells perpendicular to its surface, and fur- 

 nished with strong spiral bands, In each locellus this layer of 

 spiral cells ceases at the two lines of origin of the septum, where it 

 curves inwards a little and unites by means of smaller cells with the 

 corresponding layer of the neighbouring locellus, thus forming two 

 longitudinal ridges. The septum is therefore destitute of fibrous 

 cells ; when mature, it is composed only of a layer of interlaced 

 threads, the remains of the cells of which it was originally composed. 

 The delicate cellular membrane which clothes the whole interior of 

 the locelli in the young anther is absorbed at the moment of dehis- 

 cence. The layer of spiral cells is continued to the terminal pore, 

 the inner orifice of which it borders ; but it does not line the wall 

 of the little tube, which is formed of colourless cells, each con- 

 taining a grain of starch, whilst the cells of the plate are larger and 

 filled with a yellow liquid. Here, therefore, we have exactly the 

 reverse of what occurs in Solanum, where the fibrous cells surround 

 the pore without extending upon the inner surface of the cell. 



The mode in which the anther of Richardia emits its pollen shows 

 that it is a powerful agent of expulsion. Through each pore a white 

 thread is seen to issue and become longer by degrees, which at last 

 forms a little cotton-like ball, of a dull white colour, round the ori- 

 fice. This filament is composed of two or three parallel rows of 

 ovoid pollen-grains united by a gummy liquid ; by exposure to the 

 air, this cement evaporates, and the grains, becoming free, are dis- 

 seminated. The author considers that the contraction of the cell 

 causing this expulsion of the pollen is produced by the layer of 

 fibrous cells ; but he is unable to explain its mode of action. 



In the anther of Alocasia odora and metallica, Schott, each of 

 the two cells arranged round the dilated connective is constructed 

 nearly in the same manner ; but the cell, instead of opening upon 

 the plate itself by a duct traversing its thickness, is bent out- 

 wards and opens directly beneath the plate by an orifice common to 

 two confluent cells ; the fibrous cells predominate round the pore, 

 and several other rows are frequently added to the ordinary one at 

 the upper part of the curve. 



