Bin J. LUBBOCK — PHTTOBIOLOGICAL OBSEBTATIONS. 



397 



interesting, because it represents a case in wliieb the present 

 arrangements are not those in all respects most convenient to the 

 plant, and render it probable that the same explanation may 

 apply to other cases of difficulty. 



Fig. 13L 



Fig 132. 



Fig. 131. Seed of Oak (Qi(jrcns pechmcnlafa), Nat. size. <?, abortive ovule. 

 Fig. 132. Seed of Nut (Corylus avellana), Nat. size, o, abortive ovule. 



IVe meet indeed ■with a great many cases in which a larger 

 or smaller number of the ovules, often all bat one, fail to 

 become developed. In some of them Ave may perhaps see a pro- 

 vision to increase the chances of fertilization. There are others, 

 however, in which this exj^lanation will not hold good. In 

 Ptelea^ for instance, the ovary consists of 2-3 cells, each con- 

 taining 2 ovules, one inserted rather above the other, and tlie 

 inferior ovule constantly fails to develop. la this and other 

 similar cases we can hardly doubt that the existence of this 

 second, and now functionless, ovule carries us back to a time 

 "when the ancestors of our present Ptelea habitually produced 

 tvvo seeds. 



In Paliurus the fruit normally contains three, but sometimes 



only two loculi, each with a single seed. 



My 



the ovary is spuriously 3-celled, but the two outer cells pro- 



duce no seed. 



II<E 



tainiug a seed, only one of which, however, comes to maturity. 

 In Convallaria there are tbree cells, each with two ovules, but 

 only one of the six is generally developed. In Phillyrea there are 

 two ovules, only one of which is developed. In Canarium there are 

 two, only one of which is developed; and we meet with similar 

 cases in Gyrinopsh^ Jasmine, JEsculuSj Cprdia^ and many others. 

 From the point of view as to the origin of these differences 

 the variations in seedlings offer great interest. For example, 

 out of 135 seedlings o^Leindium sativum (which, as already men- 

 tioned, differs from the rest of the genus in having tripartite 



LINN. JOUfiN. — BOTANY, TOL. XXII. 



2ic 



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