1892. 



OUR KNOWLEDGE OF SEEDLINGS. 757 



ance of the pinnate form in the early leaves where the later are 

 reduced to the petiole (phyllodes) as in the acacia (Fig. 28). The 

 figure of a pod of Medicago orbicularis (Fig. 29), containing nine 

 germinating seeds, gives a good idea of the competition among 

 seedlings where a fruit contains several seeds, and yet does not 

 rupture. The same results where one seed contains many embryos, 

 as in Ardisiajaponica (Fig. 30). 



The variety in Leguminosae contrasts with the great similarity 

 prevailing among the seeds and seedlings of the following order, 

 Rosaceae. 



In the sun-dew [Drosera) it is interesting to find that even the 

 first leaves catch insects, though the gradation to the adult form is 

 very gradual. 



Under Viburnum (Caprifoliaceae) is described the development of 

 the lateral raphe which almost encompasses the seeds — a very 

 exceptional case in any natural order of Phanerogams. It is found 

 to result from a localisation of growth in the lower end of the young 

 seed. (Fig. 31.) The distance between the chalaza and the hilum 

 and micropyle remains unaltered, while, owing to growth of the lower 

 part oi the seed, the raphe seems to creep farther and farther round it. 



Psychotria (Rubiaceae) is remarkable in that the cotyledons are 

 provided with stipules. 



The germination is of special interest in Valerianeae and 

 Dipsaceae, where the single seed remains in the fruit, which is 

 usually capped by a membranous crown (involucel). In Scahiosa 

 australis (Fig. 32) the involucel is short and the base of the hypocotyl 

 has a sort of foot which presses against its rim, pinning it to the earth. 

 In 5. gramuntia (Fig. 33) the radicle, which here also makes its exit at 

 the upper end of the fruit, pierces the membranous lamina of the 

 involucel, fixing it to the soil by a thickening at the base of the 

 hypocotyl. 



The cotyledons of the buckwheat have the two halves unequal, as 

 in the geranium, and for the same reason, as they are curved like 

 an S i'^ the seed. The hop [Humulus) affords an interesting com- 

 parison ; the cotyledons are spirally coiled to fill the nearly globular 

 seed, but the inner has one coil more than the outer, so that after 

 germination the two are equal in length. 



A full account is given of the development of the cotyledons of 

 the w^alnut {Juglans), where they are subterranean, and its ally 

 Pterocarya, where they are aerial, the corrugated folds of the former 

 corresponding to the spreading lobes of the latter. 



The seedling of Casuarina (Fig. 34) is curious, resembling that of 

 the Gymnosperm Epliedra (Fig. 35) (Gnetaceae). 



Finally, we may notice the good series of figures illustrating the 

 germination of the water-plantain [Alisma plantago) (Fig. 36). 



We have only briefly alluded to a few of the many interesting 

 points which arise from a perusal of the text, and a comparison of the 



