THE HIGHER CRYPTOGAMIA. 173 



toms of it appear to be the production of colouring matter 

 within a spherical drop of semi-fluid mucilage. It is cer- 

 tain that no chlorophyll-vesicles pass from the original cell- 

 cavity into the enlarging protuberance. The single chloro- 

 phyll-vesicle often attains a very considerable size : in other 

 cases four or more chlorophyll-vesicles are found in the 

 protuberance before the formation of the septum which 

 divides it from the original cell-cavity. Probably these 

 have been produced by the repeated division of the original 

 individual chlorophyll-vesicle. The number of chlorophyll- 

 vesicles in the recently-formed cells of the pro-embryo is 

 very frequently four. Older cells usually exhibit a larger 

 number. It is but rarely that the chlorophyll-vesicles are 

 agglomerated in the middle of the cell : when this is the 

 case, the condition appears to me to be a diseased one. 



The well-known metallic lustre which marks the spots 

 overgrown by Schistostega is not caused by the chloro- 

 phyll-vesicles, but is fully accounted for by the spherical 

 form of the individual cells. Dew drops upon spiders' webs 

 produce a precisely similar optical appearance. 



I could not discover any nuclei in the dividing pro- 

 embryonal cells of Schistostega. My observations having 

 been made whilst travelling, I had not any tincture of 

 iodine at hand. 



Some of the older observers entertained curious opinions 

 as to the influence of the moniliform rows of cells of the 

 pro-embryo upon the development of the young plants. 

 The most peculiar notion is that of Hiibener, who says, 

 " These bodies afford, by reflexion, the light which is neces- 

 sary for the life of Schistostega ; and in this way, as Esch- 

 weiler has very correctly remarked, they represent the 

 moons of the vegetable kingdom." The glimmer of the 

 protonema of Schistostega cannot be explained by phos- 

 phorescence. The plant never shines in the dark, even 

 although previously exposed to a rather intense light, such 

 as that reflected from a white cloud. The direct action of 

 sun-light almost immediately destroys the vitality of the 

 cells. This unusual sensitiveness to the rays of the sun is 

 common to a number of other mosses also ; for instance, 

 Calypogeia Trichomanes. 



