

Chap. X. CUCTTRBITACEOUS PLANTS. 357 



but in August is in exactly the same state with them. These constitu- 

 tional peculiarities are strictly inherited. Lastly, walnut-trees, which are 

 properly monoicous, sometimes entirely fail to produce male flowers. 133 



Nuts (Corylus avellana).— -Most botanists rank all the varieties under the 

 same species, the common wild nut. 134 The husk, or involucre, differs 

 greatly, being extremely short in Barr's Spanish, and extremely long in 

 filberts, in which it is contracted so as to prevent the nut falling out. 

 This kind of husk also protects the nut from birds, for titmice (Parus) 

 have been observed 135 to pass over filberts, and attack cobs and common 

 nuts growing in the same orchard. In the purple-filbert the husk is purple, 

 and in the frizzled-filbert it is curiously laciniated; in the red-filbert the 

 pellicle of the kernel is red. The shell is thick in some varieties, but 

 is thin in Cosford's-nut, and in one variety is of a bluish colour. The 

 nut itself differs much in size and shape, being ovate and compressed in 

 filberts, nearly round and of great size in cobs and Spanish nuts, oblong 

 and longitudinally striated in Cosford's, and obtusely four-sided in the 

 Downton Square nut. 



Oucurbitaceous plants. — These plants have been for a long period the 

 opprobrium of botanists ; numerous varieties have been ranked as species, 

 and, what happens more rarely, forms which now must be considered as 

 species have been classed as varieties. Owing to the admirable experi- 

 mental researches of a distinguished botanist, M. Naudin, 136 a flood of light 

 has recently been thrown on this group of plants. M. Naudin, during 

 many years, observed and experimented on above 1200 living specimens, 

 collected from all quarters of the world. Six species are now recognised 

 in the genus Oucurbita ; but three alone have been cultivated and concern 

 us, namely, C maxima and pepo, which include all pumpkins, gourds, 

 squashes, and vegetable marrow, and C. moschata, the water-melon. 

 These three species are not known in a wild state ; but Asa Gray 137 gives 

 good reason for believing that some pumpkins are natives of N. America. 



These three species are closely allied, and have the same general habit, 

 but their innumerable varieties can always be distinguished, according to 

 Naudin, by certain almost fixed characters; and what is still more im- 

 portant, when crossed they yield no seed, or only sterile seed ; whilst the 

 varieties spontaneously intercross with the utmost freedom. Naudin 

 insists strongly (p. 15), that, though these three species have varied 

 greatly in many characters, yet it has been in so closely an analogous 

 manner that the varieties can be arranged in almost parallel series, as 

 we have seen with the forms of wheat, with the two main races of the 

 peach, and in other cases. Though some of the varieties are inconstant in 

 character, yet others, when grown separately under uniform conditions of 

 life, are, as Naudin repeatedly (pp. 6, 16, 35) urges, " douees d'une stabilite 



133 ' Gardener's Chronicle,' 1847, pp. p. 943, 



541 and 558. 135 < Gardener's Chron.,' 1860, p. 956. 



*4 The following details are taken we . Annales des Sc. Nat. Bot.,' 4th 



from the Catalogue of Fruits, 1842, in series, vol. vi. 1856, p. 5. 



Garden of Hort. Soc., p. 103 ; and from 137 < American Journ. of Science,' 



Loudon's ' Encyclop. of Gardening,' 2nd ser. vol. xxiv. 1857, p. 442. 



