218 



MONOGRAPH OF THE LABOULBENIACE^E. 



division of the basal cell, never in any case from the terminal cell, where this is pres- 

 ent. Although the products of the division of the terminal cell are invariably sterile 

 or male, it is not true, as might be supposed, that the basal cell or its derivatives have 

 any inherent female character ; since, in many cases, both normal and abnormal an- 

 theridia and antheridial branches may arise below the point of insertion of the female 

 organ, or even, in exceptional cases, replace it entirely (Plate II, figs. 7-8). While, 

 then, the primary appendage is, as a rule, terminal, the trichogyne, as well as the 

 perithecium which follows it, are always lateral, with the single exception of Amor- 

 phomyces, where both are developed terminally from the unsegmented spore. This 

 lateral origin is, however, very often obscured in the fully developed plant, from the 

 fact that the perithecium, as it develops, is apt to push the appendage more or less to 

 one side, and assume an apparently terminal position ; as, for example, in the genus 

 Stigmatomyces or in Laboulbenia. 



We have already seen that the basal cell of the germinating spore begins its 

 development by the formation of a cross partition which divides it into an upper and 

 a lower cell, and that the base of the latter becomes modified to form the foot. The 

 development of the upper, although varying considerably in the different genera, may, 

 perhaps, be best illustrated by reference to the series of figures (Plate I, figs. 1-24) of 

 Stigmatomyces, which is typical of the more simple forms. In this series, fig. 2 

 represents the spore after it has become attached to the host, the foot is beginning 

 to form and the upper half is considerably enlarged. Figs. 3-5 illustrate the further 

 development of the upper cell, the lower still remaining as at first. In fig. 6, the 

 lower cell has become divided into two superposed cells, the upper of which (b) forms 

 the basal cell of the appendage. The lower cell (y) then divides in two by a trans- 

 verse partition, forming the basal cell and the sub-basal cell (a). This sequence of 

 divisions is not apparently constant, and in other forms, at least, it more frequently 

 happens that the partition which separates (a) from the basal cell is formed before 

 that which separates (a) from (b). In fig. 7, the nucleus of cell (a) has already divided, 

 although no wall has formed between the daughter nuclei. In fig. 8, this wall has 

 been formed and the cell (a) has become divided into an upper and a lower 

 cell (a and a"), cell (b) remaining permanently without further division as the base 

 of the appendage. Of these two cells (a' and a"), the lower remains without further 

 change as the terminal cell of the receptacle ; while the upper («') alone continues to 

 develop into the female sexual organ and the perithecium. It will be noticed that 

 even at as early a stage as is represented in fig. 8, the antheridial cells have begun to 

 mature and to discharge their antherozoids. Cell (a) next begins to grow upward and 



