THE SEED PRODUCTION OF PINUS SYLVESTRIS. 9 



with that so frequently seen in connection with certain 

 fishes, where millions of eggs are without doubt fore- 

 doomed to failure — it is of an entirely different nature. 

 With the fish eggs it is reasonable to suppose that if they 

 become fertilised and nothing inimical happen, every egg 

 may become a fish ; not so, however, the Pines. In the 

 first place although each archegonium usually produces 

 four pro-embryos it is only possible that one of these can 

 arrive at maturity. In the second place we note that each 

 ovule contains about four archegonia, one only of which 

 can possibly succeed. This means that supposing the four 

 archegonia of an ovule be fertilised — it frequently 

 happens — there will be sixteen pro-embryos formed, one 

 only of which can possibly produce a seed. 



This abundant provision of female potencies is 

 exceeded — probably many thousands of times — by that of 

 the male, but it is obviously of a different character. 



What may be the significance of these peculiar pro- 

 visions on the female side for the perpetuation of the 

 species I do not know, but their existence appears to me 

 to explain some of the many difficulties that are 

 encountered in the attempt to work out the embryogeny 

 of the Pines. 



From the foregoing it is obvious that seed production 

 in Pinus sylvestris is subject to many vicissitudes, and that 

 any study made of it must bring the investigator into 

 contact with many conditions of failure, due to disease, 

 environment, enemies, abnormalities, etc. These failures 

 are evident, as changes in structure, arrested growths, and 

 alterations of sequence. The student has, therefore, to be 

 on constant guard lest the abnormal be mistaken for 

 the normal. Examples of this will be noted as we 

 proceed. 



Having now secured a general outline of the course 



