ON THE POLLEN OF MICROCACHRYS TETRAGONA 



Robert Boyd Thomson 



(WITH PLATES I AND II) 



"Microcachrys tetragona occurs only on the highest summits of tl 



Western 



William 



3.ange and Mount Lapeyrouse in Tasmania. It was intro- 

 the Royal Gardens at Kew about the year 1857 by Mr. 

 Archer, on whose property it grew. Although of great 

 interest in a botanical sense, its only value as a garden plant is for 

 conservatory decoration, for which the elegant habit it can be made 

 to assume under pot culture, its neat foliage, and bright-red fruits 

 render it highly suitable." 1 The specimens for this work were ob- 

 tained through the kindness of the present director of Kew Gardens, 

 Colonel Prain, whose courtesy and that of the staff is much appre- 

 ciated by the writer. 



The general features of the fruiting branches of microsporangiate 

 and megasporangiate plants are indicated in pi. I. The cones are 

 borne terminally and their sporophylls are spirally arranged, in 

 contrast to the opposite and slightly concrescent vegetative leaves 

 (pi. I, and pi. II, fig. 1, the branch to the left). 



The microsporophylls bear two somewhat spherical, pendant spo- 

 rangia (fig. 2), whose form and structure, after the discharge of 

 the pollen, is indicated in figs. 3 and 4. The terminal scale of the 



(fig 



(fig. 2) , very 



The inner layers of the wall are much collapsed at the stage indicated, 

 but the epidermis retains a very definite structure on account of its 

 peculiar thickened bands. These are shown in transverse and in 

 longitudinal section in figs. 5a and 5b. 



In fig. 4 some linear and branched structures are apparent in and 

 around the sporangia. These are the hyphae of a fungus, and to 

 their presence the retention of many of the pollen grains in the 

 dehisced sporangia of my material is due. The hyphae are often 



« Kent, Adolphus H., Veitch's manual of Coniferae z6r. x 9 oo. The references 

 to the discovery of this form and its description are given here. 



Botanical Gazette, vol. 47] 



[26 



