126 James Groves — A Curious Fossil Charophyte Fruit. 



A Curious Fossil Charophyte Fruit. 



By James Groves. 



THROUGH the kindness of Mr. Henry Woods, I have had the 

 opportunity of examining three blocks of limestone belonging 

 to the Sedgwick Museum at Cambridge, which were collected by 

 the late E. B. Tawney, from the " Chara Bed ", Etage Oeningien, 

 Upper Miocene, at Locle, Jura (Canton Neuchatel, Switzerland). 

 The blocks contain a number of the remains of fruits of a species 

 of Charophyte, which present a feature I had not hitherto observed, 

 and to which I think attention may advantageously be drawn. 

 Before describing this peculiarity, however, it will be desirable 

 to say something as to the conditions of preservation in which 

 such bodies are usually found. 



In living species of Chara, Lamjnotliamnium, Lychnothamnus , 

 Nitellopsis, and Tolyjyella, when the fruits are more or less mature, 

 the five spiral-cells which form the sac of the oogonium often secrete 

 a deposit of lime extremely fine and close-grained, almost j)orcelain- 

 like in texture. The lime is gradually deposited on the inner wall 

 of each spiral-cell, that is, on the side adjacent to the oospore, often 

 only partially, but in its fullest development almost entirely, 

 replacing the original protoplasmic contents of the cell. The lime- 

 contents of the five spiral-cells combine to form a firm hard shell, 

 known as the lime-shell, which envelopes the oospore, and is no 

 doubt ]3rotective in character. When the fruit becomes dry and the 

 soft part collapses, if the lime deposit is thin, each of the spiral- 

 cells appears as a rounded furrow. The concavity of the cells 

 decreases in proportion as the lime deposit thickens, becoming 

 flat or even convex when the cell is completely filled. Neither 

 the five cells forming the coronula nor the single stalk-cell 

 secrete lime. 



Apparently in almost all cases it is to the presence of such a lime- 

 shell that we owe the preservation of charophyte fruits as fossils, 

 and it is noticeable that the one living genus, Nitella, which does 

 not produce a lime-shell, is not known in the fossil state. The remains 

 of charophyte fruits, ordinarily found as fossils, consist of the sac 

 formed by the five spiral-cells only, without dther the coronula 

 or the foot-stalk, and therefore correspond with the lime-shell. 

 Occasionally the oospores are found in the sacs. We find the spiral- 

 cells in the fossils in all stages of thickness, ranging from the very 

 thin concave bands in some types, which I refer to Tolypella, to the 

 thick convex coils found in some specimens of the Chara medicaginula 

 type. 



On the interior surface of some of the fossil oogonium sacs one 

 comes across a layer of soft fine white lime of varying thickness, 

 but usually much thinner than the hard darker outer shell. In the 

 specimens of which I am writing it is in this inner layer of white 



