THE HIGHER CRYPTOGAMIA. 391 



Iii the microsporangia all the free spherical cells of the 

 interior divide at a somewhat early period into four tetra- 

 hedral special- mother-cells. The process is similar to that 

 which takes place in the division of the mother-cells of the 

 large spores of Selaginella Martensi. Four new smaller 

 nuclei are formed outside the primary nucleus of the cell, 

 apparently by the double bipartition of a spherical accumu- 

 lation of formative matter. Between each two of them the 

 six double walls appear which separate the individual special- 

 mother-cells from one another. The commissure of the 

 septa of each two special-mother-cells is often very percep- 

 tible even in the mother-cells of the small spores, notwith- 

 standing the minuteness of the object (PI. LVII, fig. 10*). 

 In each of the special-mother-cells a spore is formed, which 

 in many species (for instance in 8. Martensi) produces 

 wonderfully long spines on the outside of the exosporium 

 after the absorption of the special-mother- cells. On the 

 other hand the outer membrane of other species, such as S. 

 helvetica, appears only slightly granulated. All small spores 

 of Selaginella exhibit at the apex three converging ridges 

 of the outer spore-mernbrane. In the microsporangia of 

 cultivated tropical species of Selaginella, malformations are 

 not uncommon. Thus in S. Martensi it frequently happens 

 that a mother-cell divides into two or three special-mother- 

 cells only,* of which three, two only produce spores (PI. 

 LVII, fig. 11); or sometimes, out of a mass of special- 

 mother-cells, two or even three become shrivelled, whilst 

 the rest retain their vitality. In one case I saw the follow- 

 ing singular phenomenon. In one sporangium, containing 

 several abortive and several apparently healthy sets of 

 mother-cells, eight oval cells occurred, more than three 

 times as large as the largest special-mother-cells, and having 

 a disproportionately thick, glassy, transparent wall, which 

 exhibited manifest lamination : the cell-contents consisted 

 of concentrated granular mucilage and a rather large nucleus 

 (PL LVII, fig. 12). 



The large spores only of the Selaginellae produce pro- 

 thallia. The first rudiments of the latter are formed before 



* As in 11. Browa's Triposporium. 



