THE SEEDLING PLANT. 



stein-like portion from which the cotyledon rudiments originate, 

 and which from its position with respect to them is called the 

 hypocotyl. The process of germination of the seeds of Conifers and 

 Taxads is the same in all essential points as that of flowering plants 

 generally. When the seed is placed on damp soil of a temperature 

 sufficient to induce growth,* the endosperm or fleshy part that 

 surrounds the embryo swells and bursts the husk (testa) that encloses 

 it, splitting the testa into two parts, but which usually cohere at 

 one end. From the opposite open end the radicle or first formed 

 root protrudes and pushes its way downwards into the soil, while 

 the rudimentary stem (the tigellum or caudicle of the older botanists, 

 the hypocotyl of recent authors) lengthens in the opposite or upward 



direction, bearing at its summit the 'cotyle- 

 dons still partially enclosed in the husk 

 till it is thrown off by their further 

 lengthening and consequent tension. 

 The seedling plant then presents the 

 appearance of a rather long slender axis, 

 from the lower part of which a minute 

 rootlet has been here and there given off, 

 and terminating above in a tuft of narrow 

 leaf-like bodies, the cotyledons, which 

 vary greatly in number in different genera, 

 and in a small degree, even in the same 

 species. From the centre of this tuft 

 originates the rudiment of the future stem. 

 No trace of an epicotyl is to be seen in 

 the embryo state of Taxads and Conifers, 

 and it is not till after the development of the cotyledons into the 

 leaf-like bodies already mentioned that it appears as a prolonga- 

 tion of the hypocotyl. 



THE COTYLEDONS. The number of cotyledons varies considerably, but 

 in this respect the species readily fall into two groups, one having 



* The temperature necessary for the germination of the seeds of Taxads and Conifers has 

 not been accurately ascertained. It is, however, known that it varies in the different 

 species more or less according to the latitude of their habitat and their vertical range on 

 the mountains they inhabit. Thus, the seeds of the Siberian Larch ; the common, black 

 and white Spruces ; the Banksian, Mountain and Cembra Pines ; the alpine and common 

 Junipers, and others spreading into high latitudes or ascending to a high vertical elevation, 

 will germinate freely in a temperature ranging from 1 5 C. (34 41 F.) ; whilst the seeds 

 of those species inhabiting the warmer parts of the temperate zone require a higher 

 temperature, and those of sub-tropical species still higher. It is scarcely possible to 

 discover from the ordinary nursery practice a constant temperature for the germination of 

 the seeds of the species commonly cultivated in Great Britain, and which are usually sown 

 in the open ground Avhere the temperature may vary from day to day. The question is 

 still further complicated by the impossibility of estimating the amount of heat given out 

 by the seeds themselves during germination, which, it is known, they must do in con- 

 formity with the universal law of Conservation of Force. 



Fig. 1. Seedling plant of 

 Piceai Glelinii. 



