DIVERSITY OF HYBRIDS FROM SAME PARENTS. 559 



from the capitula selected for the experiment was not, it is true, very plentiful, but 

 some fruits invariably came to maturity. If these one-seeded fruits, all of which 

 have originated at the same time and under similar conditions, are sown, the indi- 

 viduals produced from them are but seldom like one another. The attributes and 

 external marks of the paternal and maternal stocks respectively are in some repre- 

 sented in the proportion of about 2 : 1, in others in the proportion of 1 : 2, and in a 

 third class in practically equal proportions; cases are even known where four, five, 

 or more distinct forms of hybrid have developed from the fruits of a single 

 capitulum. I found the most striking diiferences amongst the hybrids obtained by 

 crossing a capitulum of Girsium oleraceum with the pollen from a capitulum of 

 Cirsium heterophyllum. Those produced by crossing a head of Cirsium Pannoni- 

 cum with pollen from a head of Girsiwm Erisithales were scarcely less conspicuously 

 diverse. As it must be presumed that the spermatoplasm and ooplasm — or rather 

 the spermatoplasmic and ooplasmic nuclei — which have been formed in the adjacent 

 florets of a capitulum are alike in composition and ultimate structure, the variety 

 of the hybrids springing from such florets must depend solely on the relation 

 between the masses of ooplasm and spermatoplasm respectively which coalesce in a 

 flower, and the ratio between these masses must be in the one case 1 : 2, in a second 

 1:1, and in a third 2:1. Of course these ratios give but an approximate measure 

 of the degree in which each parent has participated in the generation of the inter- 

 mediate forms. Where five kinds of intermediate forms occur the series would be 

 approximately represented by the ratios 1:4, 2:3, 1:1, 3:2, and 4:1. The first 

 time flowers of a head of Cirsium Erisithales were crossed with pollen from 

 Cirsium palustre they produced two different forms of hybrid, one of which 

 approximated to the paternal, the other to the maternal stock; but no form exactly 

 midway between the two parent-stocks was obtained. A second trial of the same 

 experiment resulted in the production of a single form which did occupy this inter- 

 mediate position. These observations show that there is no definite law governing 

 the form of hybrids; one might even say that irregularity is here the rule. On one 

 occasion all the individuals which are the result of a cross between two species are 

 alike, on another occasion they constitute more or less numerous links in a chain of 

 intermediate forms. 



Hybrids which do not stand midway between the parent-species but approximate 

 to one or other of them are called goneoclinic (7'»'e'>s= parent, kUpw-I lean). That 

 such hybrids may arise from a first cross is established beyond question by the 

 experiments above recorded; but there is also another process whereby they are 

 produced, and that is the crossing of a hybrid with one of its parent-stocks. These 

 crosses are effected in great numbers, and all observers agree that in general the 

 results are better in such cases than where two species are crossed; that is to say, if 

 a hybrid's stigmas are dusted with the pollen of one of the parent-species a larger 

 number of fertile seeds may be looked for than if the plants crossed were of distinct 

 species. The individuals resulting from the cross of a hybrid with one of the parent- 

 stocks also occupy, as might be expected, a position as regards marks and attributes 



