Linnaan Society. 135 



shape and structure of the seeds of Dictyostega and some species of 

 Pleurothallis, which have both a transparent reticulated testa, show- 

 ing distinctly the included nucleus suspended from the apex. The 

 pollen of these plants also bears much resemblance to that of Or- 

 chidece, in being inclosed in a peculiar anther-case, and consisting of 

 coarse grains cohering in waxy masses. Dictyostega orobanchioides 

 also offers a beautiful illustration of the emission of pollen tubes, 

 which are seen penetrating the stigmata in crowded bundles of cot- 

 tony filaments, each thread being clavately terminated by its respec- 

 tive grain of pollen. 



There was also read a paper, entitled, " On the existence of Spiral 

 Cells in the Seeds of Acanthacece." By Mr. Richard Kippist. Com- 

 municated by Prof. Don, Libr. L.S. 



After briefly enumerating the other natural families in whose seeds 

 spiral cells had been previously observed, the author proceeds to de- 

 scribe those of a plant brought from Upper Egypt by Mr. Holroyd 

 (Acanthodium spicatum, Delile), whose peculiar appearance when 

 placed under the microscope, first led him to examine those of other 

 Acanthacece, in which family the existence of spiral cells had not be- 

 fore been noticed. The entire surface of the seed in Acanthodium is 

 covered with whitish hairs, which are appressed, and adhere closely 

 to it in the dry state, being apparently glued together at their ex- 

 tremities. On being placed in water, these hairs are set free, and 

 spread out on all sides, they are then seen to be clusters of from five 

 to twenty spiral cells, which adhere firmly together in their lower 

 portions while their upper parts are free, separating from the cluster 

 at different heights, and expanding in all directions like plumes, 

 forming a very beautiful microscopic object. The free portions of the 

 cells readily unroll, exhibiting the spire formed of one, two, or occa- 

 sionally of three fibres, which may sometimes be seen to branch, and 

 not unfrequently break up into rings. Throughout the whole length 

 of the cell the coils are nearly contiguous ; in the lower part they are 

 united by connecting fibrils, and towards the base of the adherent 

 portion become completely reticulated. The testa is a semitrans- 

 parent membrane formed of nearly regular hexagonal cells, whose 

 centre is occupied by an opake mass of grumous matter. Those 

 cells which surround the bases of the hairs are considerably elon- 

 gated, and, gradually tapering into transparent tubes, appear to oc- 

 cupy the interior of the spiral clusters. Some of these appearances 

 were noticed by Delile, who described the Acanthodium in the 

 splendid work on Egypt, published by the French Institute, where 

 also a slightly magnified figure of the seed will be found, but with- 



