180 Fanner and Digby. — Studies in Apospory and 
ferentiated on this posterior burrowing portion, and shortly afterwards the 
first cap-cell is cut off, and thus it is identified as the primary root. 
Tracheids and vascular strands are differentiated, and the embryo finally 
only differs from a normal one in the lack of a foot, and the position, 
external to the prothallium, of the stem-apex. It often happens that some 
of the prothallial cells situated near the anterior end of the embryo become 
divided so as apparently to form an additional conducting strand, con- 
necting the embryo with the stores of prothallial nutriment. This tissue 
may perhaps be regarded as physiologically representing a somewhat 
imperfect foot, but formed by the prothallium instead of the embryo. 
We have carefully examined a large number of prothallia for the 
nuclear migrations and fusions which are so constant and frequent a feature 
in the other variety of polydactyla (Wills). We have found them in 
relatively few cases (Fig. 61), and never in the wings of the prothallium. 
They have invariably occurred just behind the growing-point, and thus are 
confined to the region from which the young plantlet springs. We regard 
this fact as confirming the interpretation we have placed upon the process 
in the preceding variety, and it is of interest to find that whereas the 
migration and fusion of nuclei both occur in these two Ferns, the prothallia 
of which arise from spores, they are absent both from the common Male 
Fern, and also from all the other varieties which we have studied in which 
the prothallia were aposporously formed. 
We have endeavoured to induce apospory in this variety as well as in 
the preceding one, but hitherto without result. The methods which have 
been so successful in the case of the other Ferns that form the subject of 
this paper have entirely failed here. We have examined the nuclei of 
the embryo (Fig. 60) in this plant, and find the number of chromosomes, 
as was to be expected, to be very great. Although on account of their 
crowded condition and great numbers we were unable to arrive at exact 
estimations, we see no reason to doubt that they are present in the typical 
premeiotic number. 
The cells and nuclei of this variety, in spite of the numerous chromo- 
somes, are smaller than are those of the type (cf. p. 186 below), and a similar 
character is shared by the antherozoids. 
7. Lastrea pseudo-mas var. cristata apospora , Druery. 
This Fern owes its origin to a prothallium which came up in a Wardian 
case in which Trichomanes radicans was growing. It seems perfectly clear 
from the account 1 given by its discoverer, Mr. Druery, that the prothallium 
in question must have grown from a stray spore which had found its way 
into the case. It was, in the first instance, referred to the well-known 
Lastrea Filix-mas var. cristata , in which apogamy had already been dis- 
1 Journ. Linn. Soc., vol. xxx. 
