COTYLEDONS. 616 



into contact with the substratum. Accordingly the weather side of the trunk 

 is seen to be beset with large numbers of such seeds, and many of them, 

 pressed into the crannies of the substratum, begin to germinate. A similar 

 process is observed in the settling of the seeds of Anemone sylvestris and many 

 composites. To cite yet another example, we may name the hooked fruits of 

 Xanthium spinosum and Lappago raceTnosa. When detached from their place 

 of origin by wandering animals, these seeds remain fixed by their barbed processes 

 to the hairy coats of the animals, and thus are often removed considerable 

 distances. Naturally the animals try to free themselves from these irritating 

 appendages by rubbing themselves against the ground until they detach the 

 fruits from their coats. In this way a part of the fruits are pressed into the 

 soil, and are there anchored by their barbed spines. Only the embryos of the 

 firmly-anchored fruits develop into vigorous plants ; those seeds which lie more 

 loosely on the ground, on the contrary, either do not germinate at all, or the 

 seedlings whose cotyledons are imperfectly withdrawn from the pericarp soon 

 perish. 



Besides these outgrowths, which, as we see, possess a double function, there 

 are also those which have no connection whatever with distribution, and have 

 apparently no other use than to fasten the seeds to the germinating bed. In 

 this connection we have first to notice adhesive materials which exude from 

 the surface of the seed-husk, whereby the seeds are cemented to the soil. These 

 make their appearance when the surface of the seed is moistened, as when 

 water is sucked up by the seed from the soil of the germinating bed. Usually 

 the slimy cement arises from the superficial cells, as, for example, in the many 

 species of flax and plantain {Linum and Plantago), in the Cress and the 

 Gold-of-pleasure (Lepidium sativum and Camelina sativa), in Teesdalia, Gilea, 

 and GoUom,ia, and in many other species of the most diverse genera. All, 

 however, agree in this particular, that the seed-coat possesses a smooth, polished 

 surface. In the Basil (Ocymum Basilicum) and in the numerous species of 

 Salvia and Bracocephalum,, the mucilaginous substance arises from the smooth 

 surface of the pericarp. Frequently the adhesive mucilage is only developed 

 in certain cells arranged in rows on the surface of the fruit or seed-husk, as 

 in the New Zealand Selliera and in numerous Compositse, of which the Wild 

 Chamomile (Matricaria chamom^illa) may be cited as the best -known example. 

 In Oxybaphus there are five longitudinal ridges on the integument of the seed 

 covered with small mucilage -organs. When the integument is moistened, five 

 white slimy lines appear on it, and these bring about its adhesion to the 

 germinating bed. In many Compositse, e.g. in the common Groundsel (Senecio 

 vulgaris) and in Euriops, Doria, Trichocline, and in many other genera, special 

 hairs are developed on the fruit -husk which excrete adhesive mucilage. In 

 other instances, again, as in many aroids, the cement is not developed by super- 

 ficial cells, but a part of the fleshy pericarp, in which the seeds were inclosed, 

 remains as a dried-up crust. If these seeds be subsequently moistened, the 



