723 



LECTURE XLI. 



the connection of these shoots with their parent shoot is sooner or later destroyed by 

 the dying off and final rotting of their older parts, so that each individual shoot can 

 now grow into a new independent plant. Many Mosses, Ferns, Equisetums, Grasses 

 and Reeds, the Strawberry, and numerous other plants m&y be mentioned in this 



connection. 



It very often happens, however, that the shoots destined to become separated 

 assume special and characteristic forms, so that they may be distinguished in a 



FIG. 406. — Tetraphis pelliicida, a Moss. A a plant bearing 

 gemmae (natural size). B the same magnified ; y tlie cup in 

 which the gemmae collect. C longitudinal section through the 

 apex of .ff ; * the leaves forming the cup. K gemmae in various 

 stages of development ; the older ones are torn off from their 

 stalks by the later growth of the younger ones, and forced 

 over the edges of the cup. D a mature gemma {X 550) con- 

 sisting at the margin of one, and in the centre of several 

 layers of cells. 



Fig. 407.— Development of Tetrnphis from gcmmre. A 

 shows a gemma {b) torn off from its stalk at a \ the protoneraa- 

 filament xy has been formed by the gr9wing out of a marginal 

 cell of the gemma, and the flat structure p hJis been developed 

 as a lateral outgrowth of the protonema j this has also put out 

 root-hairs w -w' and w" {X loo). BP a flat protonema, from 

 the base of which a leaf-bud A* and root-hairs wu^ have sprung, 

 The base of the flat protonema often puts forth a number of new 

 flat protonemata before a leaf-bud is formed. 



certain sense as reproductive organs. In this connection I need only remind the 

 reader of what was said, in the lectures on Organography, concerning bulbs and tubers, 

 adding that some plants are propagated for innumerable generations solely by bulbs or 

 tubers — the potato for instance — so that reproductive organs in the narrower sense of 

 the word appear to be superfluous. In the simply organised Cryptogams (Algse and 

 Fungi) such phenomena are quite general. Deciduous cells, Conidia, are produced 

 on special supporting organs, usually in great numbers, and sometimes, as in the very 

 common mould, Penicillium glaucum, the reproduction takes place only in this way, 

 unless true reproductive organs arise under very special conditions. 



