544 Trow. —On Fertilization in the Saprolegnieae. 
species examined by me and as very probably correct in the case of the 
remaining one examined by Humphrey. 
To those who are still sceptical as to the occurrence of fertilization in 
the Saprolegnieae two questions may be put. If this remarkable succession 
concerning the number of nuclei, viz. i, 2, 1, is not evidence of normal 
fertilization, what can be the meaning of it? Are botanists prepared to 
reject all the other very numerous cases of fertilization which are founded 
on exactly analogous evidence ? Most of the proofs concerning fertilization 
in the Peronosporeae — to cite one series of cases only out of many — are 
of this character. King (’ 03 ) concludes that fertilization takes place in 
Araiospora on the basis of the demonstration of the formula 1, 2, 1. 
But the strength of the case for the occurrence of fertilization in the 
Saprolegnieae by no means rests on this demonstration of succession in 
the number of nuclei in the oospheres and oospores. It was proved, at any 
rate to my own satisfaction, that (1) the increase from one to two nuclei at 
the point of time when fertilization would naturally take place did not 
arise by division of the original single nucleus, but, on the contrary, that 
(2) the second nucleus was first noticeable at the periphery of the oosphere 
in the immediate vicinity of a fertilization-tube. Indeed, in Achlya 
americana ca 7 nbrica the tip of the fertilization-tube was traced to a point 
inside the oosphere (not the oospore) and shown to contain a single nucleus. 
These additional observations published in 1899 have not met with universal 
acceptance— indeed they have been subjected to considerable criticism by 
both Hartog (’ 99 ) and Davis (’ 03 ). 
The criticism, so far as it is relevant to the question of fertilization, is 
no doubt traceable to three sources : — (1) the incompleteness of the work, 
(2) the character of the drawings used to illustrate the papers, and (3) the 
influence of De Bary’s views as to the apogamy of the Saprolegnieae. 
Concerning the first point, nothing need be said. My only concern is 
that the work may go on towards completion — that progress may be made. 
With respect to the second, some explanation is perhaps advisable. At the 
present day it scarcely needs pointing out that every drawing, especially of 
protoplasmic structures, is of necessity more or less diagrammatic, and that 
every observer, consciously or unconsciously, decides for himself what con- 
ventional forms he shall adopt to convey to others the picture he has 
himself seen. The convention deliberately adopted by me was to draw 
every nucleus present in the actual section figured, and to take one optical 
section, out of six or seven possible ones, as a rough guide for filling in the 
cytoplasm. In the endeavour to be as realistic as possible the nuclei 
in the original drawings were not drawn boldly enough. The fine shades 
of difference in form and colour, perceptible readily enough under the 
microscope to the trained eye, when realistically copied in black and white, 
did not show sufficient contrast. The lithographer, with the original draw- 
