Apogcimy in Ferns . 185 
organs as nearly corresponding in their stages of development as we could 
get. We have reduced the value of the different cells and nuclei so as 
to express them in terms of the standard (100) given in the case of A thyrium 
Filix-foemina , which, for purposes of this comparison, we have selected 
as the type of the Athyrium series. We have also added the number 
of chromosomes. 
Ath. F.-f. var. Ath. F.-f var. Ath. F.-f var. 
Athyrium Filix- 
clarissima , 
clarissima , 
unco-glomeratum , 
foemina (type). 
Bolton. 
Jones. 
Stansfield. 
Young prothallial cells 
ICO 
135 
l8o 
250 
(near growing-point) 
Old prothallial cells 
100 
I40 
170 
30° 
(in the wings) 
Young prothallial nuclei 
TOO 
I40 
I90 
250 
Old „ „ 
IOO 
l6o 
220 
280 
Epidermal cells of leaf 
IOO 
no 
l8o 
200 
of young sporophyte 
Antherozoids 
IOO 
*35 
l6o 
250 
Number of chromosomes 
76-80 
84 
90 
IOO 
(actual number) 
(38-40 in the prothallium) 
It will be seen that there is a fairly constant difference characteristic of 
each so-called variety. It should be stated that of course the cells of the 
young parts of the prothallium are much smaller than they ultimately 
become, and that the nuclei in the older cells are likewise smaller than those 
of the cells at the growing-point. But this age-difference is tolerably 
uniform throughout the different varieties, as is indicated by the figures 
in the foregoing table. 
In the young cells we found the ratio i s * ze nuc l eus to a pp rox imate 
* 5 l size of cell ^ 
very closely to 0-32, but at a short distance behind the growing-point, 
owing to the relatively great enlargement of the cell, it diminished to 0*07 
and less. 1 It must be clearly stated that these relations only have to 
do with size, the chemical characters, such as nuclein content, having been 
left out of consideration. But taking the cell and nuclear size as the 
criterion, it will be readily seen that the so-called ‘ varieties ’ are severally 
removed from the type in the order in which they are placed in the table. 
It has been seen that the nucleolar characters differentiate them in the same 
way, and the size of the antherozoids and the number of the chromosomes 
both point in this same direction. Furthermore, the facts in connexion with 
apogamy are also in harmony with the other features. Clarissima , Bolton, 
1 Cf. Strasburger, Ueb. d. Wirkungssphare d. Kerne u. d. Zellgrosse, Hist. Beitr., v. Schwartz, 
Beitr. z. Entw. d. pflanzl. Zellkernes nach d. Theilung, Cohn’s Beitr. z. Biol. d. Pflanzen, Bd. 4. 
Gerassimow, Ueb. d. Grosse d. Zellkernes, Beitr. z. Bot. Centralbl., Bd. 18 ; also, Die Abhang. d. 
Grosse d. Zelle v. d. Menge d. Kernmasse, Zeitschr. f. allg. Physiol., Bd. 1. 
